Article

Agronomic aspects of strip intercropping lettuce with alyssum for biological control of aphids

June 2013
Biological Control 65(3):302–311

DOI:10.1016/j.biocontrol.2013.03.017

Authors:

United States Department of Agriculture

Organic lettuce growers in California typically use insectary strips of alyssum (Lobularia maritima (L.) Desv.) to attract hoverflies (Syrphidae) that provide biological control of aphids. A two year study with transplanted organic romaine lettuce in Salinas, California investigated agronomic aspects of lettuce monoculture and lettuce-alyssum strip intercropping on beds in replacement intercropping treatments where alyssum transplants replaced 2 to 8% of the lettuce transplants, and in additive intercropping treatments where alyssum transplants were added to the standard lettuce density without displacing lettuce transplants. Alyssum and lettuce dry matter (DM) were determined at lettuce maturity. Alyssum transplants produced less shoot DM in the additive than in the replacement intercropping treatments. The number of open inflorescences of alyssum increased with alyssum DM, and among treatments ranged from 2 to15 inflorescences per lettuce head. Compared with monoculture lettuce, lettuce heads on intercropped beds were slightly smaller and had lower nitrogen concentrations in the both additive treatments and in some replacement treatments. This research provides the first information on a novel additive intercropping approach to provide alyssum floral resources for biological control of lettuce aphids, and suggests that this approach may be a more land-efficient particularly for producing smaller lettuce heads for romaine hearts or for markets with less strict size requirements. Additional research is needed to determine if the increased competition between alyssum and lettuce in additive intercropping would reduce lettuce yields for wholesale markets with larger head size requirements. Practical aspects of implementing the various intercropping arrangements and alternatives are discussed. RELATED PUBLICATION http://www.ars.usda.gov/is/AR/archive/jan14/lettuce0114.htm

New Directions in Science and Environmental Communication: Understanding the Role of Online Video-Sharing and Online Video-Sharing Platforms for Science and Research Communication

Book

Full-text available

Feb 2022

In this Research Topic we are interested in the impact of online video-sharing on the public communication of science and the environment, but also on intra-scientific communication and practice. The online video format has great potential for science and environmental communication, but there are also potential problems and pitfalls that need to be reflected. We are interested in the role of online video-sharing platforms, such as YouTube, Vimeo and others, for the public communication of science and research. Production We are looking for various perspectives on the production of online videos, i.e. who creates and uploads videos with scientific and environmental contents and what are the intentions and purposes of these videos? What are the differences and similarities between professional, amateur, institutional and other actors who produce online videos? How do the different creators of videos about science and the environment legitimize themselves and what audiences do they want to reach and for what reasons? What are the differences in practices and intentions of journalists, YouTubers, scientists, scientific institutions and others when it comes to online video-sharing? Content Which scientific and environmental topics and what kinds of research and knowledge are represented in publicly available online videos and which are not? Are there certain scientific disciplines that use online videos for public and/ or intra-scientific communication more often than others? What kind of video formats, genres, videographic styles etc. are most successful, widespread and adequate for science and environmental communication? How can the quality of scientific online videos be assessed? What role do misinformation, disinformation and conspiracy theories play in online videos about scientific and environmental topics and what could be done to successfully counteract erroneous and problematic video content? Can differences concerning topics, frames or aesthetic aspects be found and analyzed, and if so how? What are the differences between the online videos of professional, amateur, institutional and other user/ producer cultures? Are there differences in the online videos from diverse geographical locations, languages and disciplinary communities? Audiences, reception and communities How are online videos on science and the environment perceived by various audiences? Do scientists and researchers also make use of the online-video format, and if so, how and why? How do different audiences make sense of the online videos they are watching and how do they affect perceptions, knowledge and attitudes? How do different users seek and find online videos about science and the environment and how do they assess the credibility of the videos? What communities emerge around specific video channels featuring science and environmental online videos and how do various audiences/ communities and video creators interact? What is the role of specific online video-sharing platforms for the dissemination, recommendation and practices of environmental and science communication via online video? Methodological innovations What quantitative, qualitative, computational and other methods could be used to study scientific and environmental online-videos and practices of online video-sharing? Practical perspectives We are also interested in perspectives of online video practitioners or researchers and others who experimented with online videos for science and environmental communication. We also welcome case studies and the experiences of science YouTubers and experience reports of exchanges with scientists, scientific institutions, journalists, filmmakers and others who use online videos for environmental and science communication. Keywords: Science Communication, Environmental Communication, Online Video, Video Platforms, YouTube, Vimeo, Public Understanding of Science, Science of Science Communication, Social Sciences, Media, Communications, Interdisciplinarity See also: https://www.frontiersin.org/research-topics/11604/new-directions-in-science-and-environmental-communication-understanding-the-role-of-online-video-sha

Intercropping With Peppermint Increases Ground Dwelling Insect and Pollinator Abundance and Decreases Drosophila suzukii in Fruit

Article

Full-text available

Oct 2021

Intercropping can be used to reduce pest insects within agricultural systems, e.g., through deterring pests directly or by increasing habitat for their natural enemies. For example, plant produced volatile organic compounds (VOCs) can deter or confuse host-finding by insects through olfactory disruption. Drosophila suzukii is an invasive fruit fly of agricultural concern as it can lay its eggs in both ripening and fresh fruits and, uses olfactory cues to identify its wide range of host plants. Peppermint plants ( Mentha × piperita ) produce high levels of VOCs while growing and may, therefore, be suitable as an intercrop to reduce D. suzukii infestations in the field, as peppermint essential oil VOCs have previously been shown to deter D. suzukii in olfactory trials. We conducted a field intercropping experiment to evaluate the effectiveness of peppermint plants compared to traditional ryegrass/clover mixes in reducing D. suzukii oviposition in the field, and the effect of peppermint intercrops on other invertebrates. In the field, we monitored sentinel fruit baits weekly for D. suzukii infestation. Additionally, we monitored intercropping effects on the invertebrate community through weekly pitfall trap collection and through a pollinator point survey. We monitored for local, farm level presence of D. suzukii through apple cider vinegar traps within crop fields and along hedgerows and found high abundance of D. suzukii (>3,000 individuals trapped). Peppermint intercrops had fewer D. suzukii emerge from fruit baits and supported greater beneficial insect abundance (predators and pollinators) compared to ryegrass/clover. However, levels of D. suzukii were low across both intercrop types. Overall, we found that peppermint intercrops could be a potential aromatic intercrop used to reduce D. suzukii adult emergence from fruit compared to conventional ryegrass/clover mixes, however this trial should be replicated over multiple growing seasons, geographic locations, and host fruits. Furthermore, further study should determine the effects of the intercrop on the focal crop of interest.

Why Should Scientists be on YouTube? It’s all About Bamboo, Oil and Ice Cream

Article

Full-text available

Apr 2021

Eric B. Brennan

Scientific information is a key ingredient needed to tackle global challenges like climate change, but to do this it must be communicated in ways that are accessible to diverse groups, and that go beyond traditional methods (peer-reviewed publications). For decades there have been calls for scientists to improve their communication skills—with each other and the public—but, this problem persists. During this time there have been astonishing changes in the visual communication tools available to scientists. I see video as the next step in this evolution. In this paper I highlight three major changes in the visual communication tools over the past 100 years, and use three memorable items—bamboo, oil and ice cream—and analogies and metaphors to explain why and how Do-it-Yourself (DIY) videos made by scientists, and shared on YouTube, can radically improve science communication and engagement. I also address practical questions for scientists to consider as they learn to make videos, and organize and manage them on YouTube. DIY videos are not a silver bullet that will automatically improve science communication, but they can help scientists to 1) reflect on and improve their communications skills, 2) tell stories about their research with interesting visuals that augment their peer-reviewed papers, 3) efficiently connect with and inspire broad audiences including future scientists, 4) increase scientific literacy, and 5) reduce misinformation. Becoming a scientist videographer or scientist DIY YouTuber can be an enjoyable, creative, worthwhile and fulfilling activity that can enhance many aspects of a scientist’s career.

insects The Future of Organic Insect Pest Management: Be a Better Entomologist or Pay for Someone Who Is

Article

Full-text available

Feb 2021

David H Headrick

Insect pest management in certified organic production systems presents considerable challenges for growers. The Federal National Organic Program (NOP) guidelines list acceptable tactics, but their effective use requires a considerable knowledgebase in entomology. The range of tactics allowed by the NOP are viewed as limiting by many growers and there are important elements missing from the list such as pest monitoring and identification. Educational programs must consider utilizing instructional methods and additional means of outreach that introduce new pest management tactics that are individualized, regionally appropriate and emphasize grower adoption and collaboration with local professionals. This review describes the challenges and knowledge burden associated with the listed NOP pest management guidelines, provides an educational model that includes an additional level of professional support for enhanced adoption of novel pest management tactics, or refinement of current practices, with a special emphasis on the importance of insect pest population monitoring.

Agronomy of strip intercropping broccoli with alyssum for biological control of aphids

Article

Full-text available

Feb 2016

Eric B. Brennan

Aromatic border plants in early season berries do not increase parasitism of spotted wing drosophila, Drosophila suzukii

Article

Sep 2022

Background: The spotted wing drosophila, Drosophila suzukii Matsumura, is a Southeast Asian vinegar fly that is a serious worldwide economic threat to the small fruit industry. Typical control consists of weekly pesticide applications, which can have non-target effects, increase residual pesticides and lead to the development of resistance within pest populations. One potential alternate method of control is the planting of aromatic intercrops to attract the natural enemies of D. suzukii and/or repel the flies directly. We intercropped strawberry rows with flowering sweet alyssum or ryegrass-clover (control) to evaluate their efficacy at mitigating D. suzukii infestation through the attraction of two specialized larval parasitoids, Leptopilina japonica (Novkovic and Kimura) and Ganaspis brasiliensis (Ihering). Results: Our study did not demonstrate any significant effect of sweet alyssum intercropping on the infestation rate of D. suzukii in strawberries or parasitism level. However, we found that advanced sampling date and recorded numbers of D. suzukii larvae and parasitoids were positively correlated, indicating higher populations at the end of the strawberry growing season. Conclusions: This is likely due to low infestation rates in early season berries or intercrops providing favourable habitat and supplemental resources for D. suzukii survival.

Native and non-native plant species differentially affect arthropod community dynamics with consequences for crop production in Lower Rio Grande Valley

Article

Dec 2022

Effects of Chemical Priming on the Germination of the Ornamental Halophyte Lobularia maritima under NaCl Salinity

Article

Full-text available

Apr 2022

Lobularia maritima or sweet alyssum (Brassicaceae) is an annual littoral halophyte, naturally thriving on sandy beaches. In addition to its obvious interest as a naturally salt-tolerant plant, this species is mainly cultivated as an ornamental plant in many countries. Laboratory experiments were carried out to assess the effects of salinity on seed germination and on germination recovery from the effects of saline conditions after transfer to distilled water. Seed germination responses were determined at 0, 50, 100, 200 and 300 mM NaCl. Salt (NaCl) does not affect the germination of L. maritima if applied at a moderate dose of 50 mM. For higher concentrations of NaCl, there is a decrease in the germination rate at 100 and 200 mM NaCl or even a total inhibition of germination at 300 mM. Salt lowers or inhibits germination only through osmotic effects. To improve the germination of L. maritima under high salinity, seeds were pretreated with KNO3, thiourea, proline and salicylic acid. The germination of seeds is improved by KNO3 in the presence or absence of salt, while thiourea increases the final germination without affecting the germination rate. Salicylic acid amplifies the effect of salt, while proline delays germination without stopping it completely. These findings indicate that the application of KNO3 and thiourea may be used to improve seed germination of L. maritima, which is of great interest for cultivating this plant for landscaping purposes in saline soils.

Altering crop management practices to promote pollinators

Chapter

Dec 2022

Agricultural intensification, or the increase in crop production per unit of input or land area to meet the needs of a growing population, has resulted in a landscape dominated by large scale monoculture cropping. Pollinators, specifically, are impacted by the lack of diverse floral and habitat resources associated with this type of farming. Agriculture must develop practices that diversify the crop landscape and increase the availability of habitat and flowering resources to support these populations. In this chapter, we summarize the available literature on how the production space, i.e., within a crop production field, orchard, or pasture, can be more effectively managed to sustain pollinator populations. We report on various spatial and temporal approaches within the context of various cropping systems (row crops, specialty crops, perennial orchards, and perennial forage and pasture systems). Collectively, these approaches represent opportunities to re-introduce diversity into the agricultural landscape to benefit pollinators.

Intercropping with service crops provides multiple services in temperate arable systems: a review

Article

Jun 2022

Service crops are crops grown to provide services to other cash crops, rather than for production purposes, with the ultimate aim of improving the environmental and production performances of cropping systems. Service crops can be intercropped with cash crops to facilitate interactions between crops and to optimize the use of the cropping season. Many terms exist to describe these practices, which highlights their diversity. However, this diversity of terms may be a source of confusion. Here, we present an overview of the current uses of intercropped service plants in temperate cropping systems, with the main services they provide and their management. (1) First, we show that a limited range of service crop species, mostly from the Fabaceae family, have been studied to date. This finding suggests that the diversity of species and cultivar resources that can be used as service crops has been poorly explored in the literature. In contrast, the combinations of service and cash crops tested appear wider. We address this diversity by defining synchronous intercropping, living mulch and relay intercropping. (2) Then, we show that intercropped service crops can efficiently reduce weed biomass and pest attacks and improve nitrogen cycling, thereby increasing soil fertility and improving crop nutrition. The intensity of these services is positively associated with service crop biomass, but excessive service crop biomass increases the risk of competition with cash crops. (3) The balance between the services and disservices provided can primarily be interpreted in terms of biomass production of coexisting crops. The resulting effect of service crops on cash crop yield is variable and reflects the integration of the effects of the various individual services, together with possible disservices. (4) The diversity in management methods makes it possible to manage this trade-off and to adapt the system to different conditions with a few tested species.

Intégration de la Cameline au sein des agro-écosystèmes : des relations multi-trophiques complexes

Thesis

Dec 2016

Quentin Chesnais

La cameline, Camelina sativa (Brassicaceae), fait aujourd'hui l'objet d'un regain d'intérêt. Il s'agit d'une plante aux vocations multiples (bioénergétique, industrielle, alimentaire), aux exigences agronomiques faibles et qui semble peu sujette aux attaques de ravageurs phytophages.Trois objectifs visant à appréhender la complexité des interactions multitrophiques autour de la cameline ont été définis au cours de ce travail de thèse. Le premier visait à déterminer le rôle de la cameline en tant que réservoir à pucerons ravageurs. Les deux autres reposaient sur les études des impacts des pratiques culturales (fertilisation azotée, culture en association) et des virus de plantes, sur les interactions tritrophiques cameline/pucerons/parasitoïdes. Les premiers résultats ont permis de montrer que la cameline pouvait être considérée comme plante réservoir pour différentes espèces de pucerons ravageurs présents dans les paysages agricoles du nord de la France, qu'il s'agisse d'espèces inféodées aux Brassicaceae (Brevicoryne brassicae), d'espèces polyphages (Myzus persicae, Aphis fabae) ou encore d'espèces spécialistes des Poaceae (Rhopalosiphum padi). En ce qui concerne les deux pratiques culturales étudiées, l'association de la cameline avec la fèverole a engendré des effets délétères sur le contrôle biologique du puceron Aphis fabae par le parasitoïde Aphidius matricariae. Le comportement des femelles A. matricariae ne semble pas satisfaire à la théorie de "l’optimal foraging". En parallèle, des effets de la fertilisation azotée ont été observés sur les trois niveaux trophiques et ont varié en fonction de la dose apportée à la plante et du degré de spécialisation du puceron. Ainsi, notre étude montre que les pratiques culturales peuvent avoir des répercussions importantes de type "bottom-up" sur les niveaux trophiques supérieurs. Enfin, nous avons montré un impact des deux virus de plantes étudiés qui s'est révélé variable non seulement en fonction du mode mais aussi de l'efficacité de la transmission par le puceron-vecteur. Ce dernier travail a également permis de mettre en évidence des effets "bottom-up" d'un virus sur le comportement de sélection de l'hôte par un parasitoïde de puceron mais aussi sur la physiologie des partenaires appartenant aux trois niveaux trophiques. En effet, les performances du puceron-vecteur sur la plante infectée semblent améliorées alors que celles du parasitoïde sont altérées, ce qui pourrait se traduire par une meilleure propagation du virus. Ces travaux soulignent l'importance de la prise en compte des relations multitrophiques avant la (ré-) introduction d’une espèce de plante dans les agro-écosystèmes, et en particulier l'intérêt d'identifier les risques associés en termes de pression de ravageurs et de pathogènes

Evaluation en laboratoire du parasitoïde Gryon gonikopalense (Hym : Scelionidae) pour le contrôle biologique de Bagrada hilaris (Hem : Pentatomidae), une punaise invasive aux Etats-Unis

Thesis

Sep 2021

Guillaume Martel

In a context of globalization and climate change, more and more insects are becoming invasive, particularly affecting agriculture on a global scale. At the heart of this network of invasions, the United States of America is experiencing the arrival of many species, mainly from Asia. Among them, stink bugs (Pentatomidae) threaten most American agrosystems and are now mainly regulated by synthetic pesticides. Bagrada hilaris (bagrada), native to Asia and Africa, is the most recent species to invade the USA, where it has been reported since 2008 in Brassicaceae crops. To answer the needs of farmers, USDA-ARS funded a classical biological control program to select and introduce from its native range one or more natural enemies of bagrada into California. The research included in this PhD thesis is part of this program. It sought to assess in a quarantine greenhouse whether the oophagous parasitoid Gryon gonikopalense (Scelionidae), native to Pakistan, could establish in California and efficiently control bagrada. Thus, four main objectives were defined: 1) to describe the general biology of G. gonikopalense; 2) describe its host foraging behavior; 3) examine the possibility of its mass production and 4) assess its specificity towards bagrada using Euro-Mediterranean non-target stink bugs. Objective 1 allowed to show that the physiology of G. gonikopalense was similar to that of many other scelionids: depending on the temperature, it completed its development in 7 to 25 days, its lifespan ranges from 30 to 150 days and it is able to parasitize hundred eggs during its lifetime. It shares with bagrada a thermal optimum between 25 and 35 °C which could allow it to settle in California. In addition to being an effective parasitoid of bagrada, the advantage of G. gonikopalense particularly involves its foraging behavior for host's eggs, which are buried in the ground in 90% of cases. We found that G. gonikopalense was able to dig into the soil to parasitize eggs. In addition, we have shown in a tri-trophic system that the parasitoid mainly attacks the buried eggs of bagrada, while being able to reach the eggs deposited on the host plant (about 10%). For the 3rd objective, we have shown that the storage of bagrada eggs at 5 °C over three weeks made it possible to optimize the breeding of the parasitoid and facilitate mass production. Concerning the objective 4, still in progress, we showed that among the 11 pentatomids tested, at least four were suitable for the parasitoid, and two of them were mainly located around the Mediterranean basin. These results complement the tests carried out in California and open a proactive discussion on the introduction of G. gonikopalense in invasive Mediterranean populations of bagrada. Finally, during this thesis, we have described several aspects, hitherto unknown, of the biology of G. gonikopalense. Its behavioral specialization towards bagrada makes this parasitoid particularly promising for the biological control program. A petition-to-release drafted on the basis of this knowledge submitted to the health authorities of the USA remains a short-term objective. They will then assess the risks and benefits of using G. gonikopalense to control bagrada in California.

A comparison of wild bee communities in sown flower strips and semi‐natural habitats: A pollination network approach

Article

Full-text available

Jan 2022

• Drastic reductions of insect diversity and abundance have been observed in highly fragmented agricultural landscapes of central Europe. Declines of pollinators may have detrimental effects on the reproduction of wild insect-pollinated plants as well as the yield of crops. In order to mitigate such impacts, sown flower strips on arable land within Agri-Environment Climate Schemes (AECS) are supported across EU countries. However, it is not clear whether sown flower strips provide equivalent benefits to wild flower-visiting insects as semi-natural habitats. • Here, we apply plant–pollinator network approach to evaluate the function of sown flower strips for the communities of wild bees. We compared the structural characteristics and the robustness of plant–pollinator networks in sown flower strips and nearby semi-natural habitats in seven sites in the Czech Republic. We also quantified the importance of individual plant species for bees based on simulations of plant–pollinator extinction cascades. • We found that assemblages of plants and pollinators were less diverse in sown flower strips than in semi-natural habitats, more generalised, and more nested. However, we did not find any significant differences in network robustness to plant–pollinator coextinctions. Further, simulations revealed large variation in the functional importance among plant species from both habitats. • We conclude that although the analysis of network robustness suggested that plants in the sown flower strips and semi-natural habitats were functionally equivalent, this masked important differences between the two habitats. From a conservation point of view, semi-natural habitats were superior in supporting a more diverse community of solitary bees and bumblebees, likely because of their greater longevity and higher habitat heterogeneity.

Control biológico de pulgones

Chapter

Full-text available

Aug 2021

El presente capítulo tiene como objetivo brindar aspectos generales de las especies a las que se atribuyen las mayores pérdidas de rendimiento y calidad de los cultivos hortí-colas y los principales controladores biológicos que limitan sus poblaciones, ejer-ciendo un control biológico de manera natural.

Control Biológico por conservación

Chapter

Full-text available

Aug 2021

En el presente capítulo se exponen los principios y estrategias del manejo de hábitat, así como estudios de casos en los que se aplica a los sistemas hortícolas.

Are plants in sown flower strips suitable for communities of wild bees? Pollination network approach in conservation biology

Preprint

Full-text available

May 2021

Drastic reductions of insect diversity and abundance are observed in the highly fragmented agricultural landscapes of central Europe. Declines of pollinators may have detrimental effects on the reproduction of wild insect-pollinated plants as well as the yield of crops. In order to mitigate such impacts, sown flower strips on arable land within Agri-Environment Climate Schemes (AECS) are supported across EU countries. However, it is not clear whether sown flower strips provide equivalent benefits to wild flower-visiting insects as semi-natural habitats. Here, we apply plant-pollinator network approach to evaluate the function of sown flower strips for the communities of wild bees. We compared the structural characteristics and the robustness of plant-pollinator networks in sown flower strips and nearby semi-natural habitats. We also quantified the importance of individual plant species for bees based on simulations of plant-pollinator extinction cascades. We found that assemblages of plants and pollinators were less diverse in sown flower strips than in semi-natural habitats, more generalized, and more nested. However, we did not find any significant differences in network robustness to plant-pollinator coextinctions. Further, simulations revealed a large variation in the functional importance among plant species from both habitats. We conclude that although the analysis of network robustness suggested that plants in the sown flower strips and semi-natural habitats were functionally equivalent, this masked important differences among the two habitats. From the conservation point of view, semi-natural habitats were superior in supporting a more diverse community of solitary bees and bumblebees.

Sparrow Preferences for Winter Cover Crops in California's Central Coast

Article

Full-text available

Nov 2020

Eric B. Brennan

Agriculture in many regions of the world has reduced bird habitat and abundance, and altered avian community structure. A study was conducted on an organic research farm over two winters (Oct to Mar) in an intensive agricultural region of Salinas Valley, CA to determine how cover crop variety and planting density influenced birds. Cover crops were rye (Secale cereale), a mixture of rye and legumes (Vicia spp., Pisum sativum), and a mustard mixture (Brassica juncea, Sinapis alba). White-crowned Sparrows (Zonotrichia leucophyrs), Savannah Sparrows (Passerculus sandwichensis) and Song Sparrows (Melospiza melodia) were observed both years in the study field. Bird droppings in cover crops were quantified and dissected to determine dietary preferences, and sparrow movement when flushed was determined. Dropping number and weight per m2 were at least 10 times greater in mustard than in rye and in the legume-rye mixture. Droppings were dominated by leaf tissue in mustard vs. arthropod tissue in rye and legume-rye. Within cover crop variety, plant density did not have a clear or consistent effect on sparrows. Sparrows flushed from cover crops usually settled in mustard. The White-crowned Sparrow fed on mustard leaves and apparently on weed foliage under mustard. The arthropod-dominated droppings in rye and legume-rye cover crops were consistent with the food preferences of Song and Savannah Sparrows. The White-crowned Sparrow's clear preference for mustard cover crops is likely due in part to their high dietary needs for sulfur-rich amino acids during the prenuptual molt. This paper provides novel information to help farmers and others understand the cover crop preferences of sparrows, and ways that farmers might use mustard cover crops as trap crops to reduce White-crowned Sparrow feeding damage on winter and spring vegetable crops. It also provides evidence of ecosystems services that these sparrows provide by feeding on weed tissue in winter cover crops.

Insecticidal and repellent efficacy of the essential oil from Lobularia maritima and trans -3-pentenenitrile against insect pests of stored grains

Article

Full-text available

Jan 2020

The essential oil from the aerial parts of Lobularia maritima was investigated for its chemical composition, and its repellent and insecticidal efficacy against the grain pests Callosobruchus maculatus, Tribolium castaneum and Sitophilus oryzae. A number of 41 compounds were identified by GC-MS from which azeleonitrile (39.7%), trans-3-pentenenitrile (36.3%) and 4-isothiocyanato-1-butene (10.9%) were the most abundant. A fumigant bioassay-guided fractionation of the essential oil constituents led to the isolation of trans-3-pentenenitrile. Its structure was confirmed by EI-MS and NMR techniques. Fumigant effect of the essential oil was strong (LC50 = 7.48 μL/L) on C. maculatum and moderate on S. oryzae and T. castaneum (LC50 = 35.37 and 59.94 μL/L, respectively). trans-3-pentenenitrile showed strong fumigant effect on the three pest species (LC50 = 6.62–8.36 μL/L). Both the oil and trans-3-pentenenitrile showed strong contact effect with LD50 values in the range 4.84–7.81 µg/adult. The oil showed a repellency of 100% on C. maculatus and S. oryzae at concentrations higher than 0.05 and 0.1 nL/cm², respectively, and 93% against T. castaneum yet at 0.2 nL/cm². trans-3-pentenenitrile also showed 100% repellency against C. maculatus (≥ 0.05 nL/cm²), S. oryzae (≥ 0.15 nL/cm²) and T. castaneum (0.2 nL/cm²). The results in this study indicated that the essential oil of L. maritima is an important source of trans-3-pentenenitrile which can be used in the development of insecticidal agents against the three grain pests.

Response surface methodology reveals proportionality effects of plant species in conservation plantings on occurrence of generalist predatory arthropods

Article

Full-text available

Apr 2020
PLOS ONE

Multivariate geometric designs for mixture experiments and response surface methodology (RSM) were tested as a means of optimizing plant mixtures to support generalist predatory arthropods. The mixture design included 14 treatment groups, each comprised of six planters and having a proportion of 0.00, 0.17, 0.33, 0.66, or 1.00 of each plant species. The response variable was the frequency of predators trapped on sticky card traps placed in each group and replaced 2 times per week. The following plant species were used: Spring 2017: Euphorbia milii, E. heterophylla, and Phaseolus lunatus; Summer 2017: E. milii, Fagopyrum esculentum, and Chamaecrista fasciculata; and, Summer 2018: E. milii, F. esculentum, and Portulaca umbraticola. Predator occurrence was influenced by: 1) Linear mixture effects, which indicated that predator occurrence was driven by the amount of a single plant species in the mixture; or, 2) Nonlinear blending effects, which indicated that the plant mixture itself had emergent properties that contributed to predator occurrence. Predator abundance was highest in the Spring 2017 experiment and both linear mixture effects and nonlinear blending effects were observed. Predator occurrence decreased in subsequent experiments, which were conducted in the warmer summer months. In both Summer experiments, only linear mixture effects were observed, indicating that predator occurrence was driven by the amount of a single plant species in the test mixtures: Euphorbia milii in 2017 and Portulaca umbraticola in 2018. The results showed that not only did the species composition of a plant mixture drive predator occurrence but that proportionality of species contributed to the outcome as well. This suggests that, when formulating a plant mixture to aid in conservation biological control consideration should be given to the proportion of each plant species included in the mixture. RSM can be an important tool for achieving the goal of optimizing mixtures of plants for conservation biological control.

Strip intercropping peanut with maize for peanut aphid biological control and yield enhancement

Article

Sep 2019
AGR ECOSYST ENVIRON

Evaluation of land productivity, competition and insect diversity in different intercropping patterns of sunflower (Helianthus annuus L.) and soybean (Glycine max L.) under low-input condition

Article

Full-text available

Jan 2018

Intercropping is a sustainable practice to achieve higher production with the aim to limit external inputs. A field experiment was conducted at the research farm of the Faculty of Agriculture, University of Maragheh, Maragheh, Iran, during 2016 growing seasons with ten treatments to evaluate the yield, analyze the competition and insect's assemblages in sunflower (as main plant)/soybean (as companion plant) intercropping. Treatments included sunflower sole cropping, soybean sole cropping, replacing intercropping sunflower with soybean (50:50, 34:66, 66:34, 40:60, 60:40, 25:75) and additive intercropping of two plants (100:50 and 100:100%). Results showed that the highest sunflower grain yield (275 g m-2) was obtained in sunflower monoculture that was not significantly different with intercropping ratios of 25:75 and 60:40. Also, the highest and lowest grain yield of soybean was achieved in soybean monoculture (130.1 g m-2) and ratio of 100:50 (48.5 g m-2), respectively. The highest land equivalent ratio, monetary advantage index and intercropping advantage value was obtained in intercropping ratio of 25:75. Moreover, in all cropping patterns the aggressivity (A) and crowding ratio (CR) values of sunflower were higher than soybean, indicating that sunflower was the dominant species. Also, the highest density for herbivores was recorded in soybean monoculture and the families of Thripidae (37.60-43.87%) and Cicadellidae (34.01-37.71%) had the most relative density. Furthermore, intercropping of sunflower with soybean increased pollinators and natural enemies' abundance compared with monocultures. Overall, based on the ecological, agronomical and economical indices intercropping sunflower with soybean with ratio of 25:75 is a feasible alternative method to achieve similar production with respect to monocropping.

SALAH WF NOT YET

Article

Jul 2019

Weed floral resources are often overlooked in biological control manipulations, yet common species in this group can contribute to enhanced biological control efficacy. Weed floral resources may not be examined as frequently as certain insectary species (buckwheat). Furthermore, they may require less maintenance and are adapted to grow in the planted area. Here, we investigated the effects of weed and other non-crop floral resources on Eretmocerus mundus, a parasitoid of the whitefly, Bemisia tabaci, in the laboratory. The two common weeds evaluated were shepherd’s purse (Capsella bursa-pastoris) and white rocket (Diplotaxis erucoides). These were compared with buckwheat (Fagopyrum esculentum) and alyssum (Lobularia maritima). Adults of the above parasitoid were exposed to flowers of the selected plants and survived 6 times longer with buckwheat than those in the control (water only) and 2.8, 3.1 and 4 times longer with shepherd’s purse, rocket and alyssum, respectively. All plant species significantly increased parasitoid longevity, egg load and fecundity compared to the control. Buckwheat had the greatest effect on these parameters. Parasitism rate of the pest increased by up to 72.1%. This work illustrates that the selected non-buckwheat species could have value where buckwheat germination rate and phenology may be limiting such as in arid climates, for which this work was targeted.

Weed floral resources and commonly used insectary plants to increase the efficacy of a whitefly parasitoid

Article

Jul 2019

Weed floral resources are often overlooked in biological control manipulations, yet common species in this group can contribute to enhanced biological control efficacy. Weed floral resources may not be examined as frequently as certain insectary species (buckwheat). Furthermore, they may require less maintenance and are adapted to grow in the planted area. Here, we investigated the effects of weed and other non-crop floral resources on Eretmocerus mundus, a parasitoid of the whitefly, Bemisia tabaci, in the laboratory. The two common weeds evaluated were shepherd’s purse (Capsella bursa-pastoris) and white rocket (Diplotaxis erucoides). These were compared with buckwheat (Fagopyrum esculentum) and alyssum (Lobularia maritima). Adults of the above parasitoid were exposed to flowers of the selected plants and survived six times longer with buckwheat than those in the control (water only) and 2.8, 3.1 and four times longer with shepherd’s purse, rocket and alyssum, respectively. All plant species significantly increased parasitoid longevity, egg load and fecundity compared to the control. Buckwheat had the greatest effect on these parameters. Parasitism rate of the pest increased by up to 72.1%. This work illustrates that the selected non-buckwheat species could have value where buckwheat germination rate and phenology may be limiting such as in arid climates, for which this work was targeted.

Effect of Tomato Rootstock on Hybrid and Heirloom Tomato Performance in a Midwest High Tunnel Production System

Article

May 2019
HORTSCIENCE

High tunnels allow vegetable growers to extend the growing season, increase crop production, and improve produce quality. Tomatoes ( Solanum lycopersicum L.) are the most widely grown crops in high tunnels; however, tomato production in high tunnels can be challenging. Continuous cropping in high tunnels can increase soil-borne disease pressure and can lead to soil salinity or nutrient depletion issues. Based on preliminary research, we hypothesized that use of the rootstock ‘RST-04-106-T’ would increase yield and quality of heirloom and hybrid tomato scions compared with nongrafted plants. To test this hypothesis, our research objectives were to assess marketable yields, fruit quality and nutritional value, and plant growth of grafted and nongrafted hybrid and heirloom tomatoes in a high tunnel production system. Grafted and nongrafted ‘Cherokee Purple’ (heirloom) and ‘Mountain Fresh Plus’ (hybrid) tomatoes were grown in the same high tunnel for two seasons (7 May–20 Oct. 2015 and 29 April–7 Oct. 2016) at the Horticulture Research Station in Ames, IA. Grafted plants produced significantly more marketable fruit, although marketable and total fruit weight did not increase significantly. Individual fruit size was unaffected by grafting. Across cultivars, mean soluble solids content (SSC) in fruit was 0.3 °Brix lower in grafted plants as compared with the nongrafted control. Grafting did not affect lycopene content of fruit. Grafting increased stem diameter by an average of 0.8 mm, but overall plant biomass was unaffected. The effect of grafting on leaf chlorophyll concentration (SPAD readings) was mixed. In addition, grafting increased leaf chlorophyll concentration in ‘Cherokee Purple’ but decreased it in ‘Mountain Fresh Plus’ plants. Grafting is a valuable tool in tomato production, but the impact of ‘RST-04-106-T’ rootstock use appears to be specific to certain soil types with high incidence of bacterial wilt.

Use of Parasitoids as a Biocontrol Agent in the Neotropical Region: Challenges and Potential

Chapter

Full-text available

Nov 2018

The Slide Hammer Seeder: A Novel Tool for Planting Small Seeds

Article

Full-text available

Dec 2018
HORTTECHNOLOGY

Eric B. Brennan

Many important herbs [e.g., mint ( Mentha sp.), thyme ( Thymus sp.)], underused and nutritious vegetables [e.g., purslane ( Portulaca oleracea), amaranth (Amaranthus tricolor )], and important biological control plants [e.g., sweet alyssum ( Lobularia maritima )] have small seeds (≤ 1.5-mm long) that are difficult to plant with raw (i.e., nonpelleted) seed using existing seeders. A novel tool known as the slide hammer (SH) seeder was developed for the precise seeding of raw seeds of small-seeded plants. The SH seeder is a jab-type planter made primarily from electrical conduit tubing and other materials that are inexpensive and readily available in a hardware store or on the Internet. The interchangeable seed hopper is made from a plastic snap cap vial that has one or more holes of varying diameter depending on the desired seeding rate and seed size. Seed forms a “bridge” above the hole in the vial until they are dislodged from the force of the SH that discharges seeds to fall to the soil. Detailed plans are provided for how to make and use the SH seeder. The fabrication time is 2 to 4 hours with a material cost of ≈$32. I determined the seed vial hole specifications for the precise seeding of a variety of small-seeded plants, including chives ( Allium schoenoprasum ), chinese chives ( Allium tuberosum ), basil ( Ocimum basilicum ), grain amaranth ( Amaranthus sp.), sweet alyssum, purslane, creeping thyme ( Thymus serpyllum ), and spearmint ( Mentha spicata ) that ranged in size from ≈200 to 11,000 seeds per gram. The diameter of the hole that was suitable for discharging the seed from the vial was always larger than the average seed length, and the ratio of hole diameter to seed length ranged from 1.07 to 1.62. Seeding rate uniformity evaluations were conducted for these species using vials with one vs. two holes and showed that the seeding rate was higher by an average of 58% to 173% from a vial with two holes compared with one hole. For most plant species evaluated, the SH seeder was able to dispense as few as one to three seeds consistently. Seed discharge increased somewhat with increasing SH weight for all species evaluated. The SH seeder can be useful for interplanting sweet alyssum as an insectary plant for aphid (Aphidoidea) control between existing plants of organic lettuce ( Lactuca sativa ), and for intercropping cultivars of purslane as a novel vegetable in between transplanted organic broccoli ( Brassica oleracea Italica group) plants. This novel seeding tool has many potential uses for direct, hand seeding in vegetable and herb production systems and in weed research trials. The seeder could be automated and made with a variety of alternative materials.

Engineering natural enemy shelters to enhance conservation biological control in field crops

Article

Oct 2018

Lessando M. Gontijo

Conserving natural enemies has become the cornerstone for sustainable pest management. Conservation is often attained through habitat manipulation in order to create suitable conditions for supporting the populations of natural enemies. In this context, creating natural enemy shelter is an important tactic for enhancing the conservation biological control of pests. In this article, I have reviewed several aspects of sheltering natural enemies, including the ecological mechanisms that promote conservation biological control, potential negative interactions, and directions for creating shelters, in addition to indicating challenges and recommendations for future work. Shelters may bolster natural enemy abundance/diversity by providing them with suitable microclimate, alternative prey/host, and non-prey food, in addition to providing protection from intraguild predators and pesticides. However, a shelter may interact negatively with natural enemies in some instances by hampering their movement, diverting their attack, and/or promoting antagonistic intraguild interactions. Some of the most common forms of shelters include beetle banks, shelterbelts, hedgerows, flower strips, intercropping, and selective conservation of arable weeds. Nonetheless, while these habitat manipulations have been proven to be beneficial, many challenges still lie ahead. We need to promote adoption of conservation biological control by farmers, especially by scientifically linking its implementation to profitability (i.e., crop yield). Additionally, an interdisciplinary research approach is necessary for the development of an applied knowledge concerning how the interplay between local management, landscape complexity, and arthropod community will affect conservation biological control of herbivorous pests. Because this type of knowledge is important for the environment and sustainable agriculture, more programs that foster conservation biological control should be incentivized by governments.

Occurrence of Coccinellids that Prey on Diaphorina citri (Hemiptera: Liviidae) on Euphorbia heterophylla (Euphorbiaceae) and Chamaecrista fasciculata (Fabaceae) in a South Florida Residential Area

Article

Full-text available

Mar 2018

Joseph Patt

Adding plant-based nutritional resources to a landscape may help to recruit and retain predaceous and parasitic arthropods. As a first step in determining whether the addition of nectary plants can increase the abundance and diversity of biocontrol agents of Diaphorina citri and psyllid suppression in urban and unmanaged landscapes in southern Florida, the occurrence of coccinellids was recorded on a native poinsettia, Euphorbia heterophylla (L.) and partridge pea, Chamaecrista fasciculata (Michx.) Greene, a native legume. Thirteen coccinellid species consisting of a total of 663 specimens were collected over the course of the 8-mo long sampling period. A total of 464 specimens comprising 12 species were collected from E. heterophylla from Jun to Oct, with 3 species, Coelophora inequalis, Cryptolaemus montrouzieri, Harmonia axyridis, comprising the majority of species collected. A total of 199 specimens comprising 6 species were collected from C. fasciculata from Sep to Feb. Nearly 80% of the specimens collected from C. fasciculata were C. montrouzieri.

ABCopinion

Article

Mar 2018

J.P. Michaud

Intercropping Halophytes to Mitigate Salinity Stress in Watermelon

Article

Full-text available

Mar 2018

Saline irrigation water can lead to salt buildup and reduced crop yields. Halophytic plants are known to accumulate excess salts in tissues, removing them from the immediate environment. This two-phase experiment explored the feasibility of intercropping watermelon (Citrullus lanatus (Thunb.) Matsum. and Nakai var. lanatus) with halophytic species to mitigate the negative effects of saline irrigation water while providing a value-added crop. In the first experiment, six greenhouse-grown species were irrigated with water that was either deionized (0 dS m⁻¹) or contained 3 or 6 dS m⁻¹ of salts for 41 days and screened for growth and salt removal. Two halophytes were selected to be additively intercropped with watermelon under field conditions and irrigated with the same saline irrigation levels as the first experiment. Results indicated that garden orache (Atriplex hortensis L.) exhibited the highest growth rates and purslane (Portulaca oleracea L.) accumulated high amounts of sodium in plant tissues under saline irrigation. The field experiment showed that watermelon yields, stem water potential, and fruit quality were not affected by saline irrigation; however, the watermelon/orache intercropping treatment had significantly higher yields. These results suggest intercropping with halophytes has the potential to contribute a value-added crop without reducing watermelon yields.

Problems Inherent to Augmentation of Natural Enemies in Open Agriculture

Article

Jan 2018

J.P. Michaud

Augmentation biological control has successfully replaced a lot of insecticide use in 'closed system' agriculture (e.g., greenhouses). The profitable commercialization of biocontrol agents in greenhouses has created an incentive to expand markets for mass-reared beneficial insects into open agricultural systems, often without sufficient scientific justification. However, the semi-contained nature of greenhouse culture is often critical to the success of augmentation and can serve to mask potential pitfalls and intrinsic limitations of this approach in open systems. Factors contributing to greenhouse successes include the reduced biological diversity of contained agroecosystems, the prevention of agent dispersal, the ability to maintain environmental conditions within a range favorable for the agent, the exclusion of competitors and natural enemies of the agent that might otherwise diminish its efficacy, and the absence of alternative prey/hosts that could divert predation/parasitism from the target pest. There are also problems arising from collection of source material from locally adapted populations, and the inadvertent imposition of artificial selection in the course of laboratory rearing. Besides highlighting these pitfalls, this paper aims to encourage more consideration of conservation approaches prior to investment in augmentation programs which entice farmers into perpetual cycles of 'rear and release.' I argue that although augmentation can benefit agriculture whenever it replaces pesticide applications, it does not constitute an ecologically sustainable solution because it requires continued inputs, and it can distract research attention away from more sustainable objectives. Sustainable biological control is best achieved through modifications to cultural practices that increasingly 'naturalize' agroecosystems, thus facilitating the natural recruitment and persistence of beneficial arthropod fauna, combined with habitat management geared to increasing overall plant and arthropod diversity in the agroecosystem.

Attraction of Aphidius ervi (Hymenoptera: Braconidae) and Aphidoletes aphidimyza (Diptera: Cecidomyiidae) to Sweet Alyssum and Assessment of Plant Resources Effects on their Fitness

Article

Jan 2018

The green peach aphid Myzus persicae (Sulzer) (Hemiptera: Aphididae) is one of the most economically important aphid species affecting crops worldwide. Since many natural enemies of this aphid have been recorded, biological control of this pest might be a viable alternative to manage it. Selected plant species in field margins might help to provide the natural enemies with food sources to enhance their fitness. This study aimed to investigate if sweet alyssum, Lobularia maritima (L.) (Brassicaceae), is a potential food source for the parasitoid Aphidius ervi Haliday (Hymenoptera: Braconidae) and the predator Aphidoletes aphidimyza (Rondani) (Diptera: Cecidomyiidae), and whether this flower could contribute to enhance the biological control of M. persicae. Volatiles produced by alyssum, with and without flowers, attracted both natural enemies. This attractiveness to alyssum flowers was disrupted when compared with peach shoots recently infested with a relatively low number of aphids. When aphids were absent, parasitoids exposed to alyssum survived longer than those that fed on a sugar solution or on water. In the case of the predator, alyssum flowers did not benefit longevity since the nectaries were inaccessible to females. However, our results provide evidence that A. aphidimyza would be able to feed on nectar if accessible. The floral resource did not improve the reproductive capacity of the two natural enemies, but the 10% sugar solution increased the egg load of the predator. Provision of other sugar resources, such as flowers with exposed nectaries and extra floral nectar may also be a viable option to improve the biological control of M. persicae.

Spatio-temporal dynamic of insect pests and flower flies in agroecological lettuce associated with alyssum (Lobularia maritima)

Conference Paper

Full-text available

Oct 2017

Laboratory Evaluations of the Foraging Success of Tamarixia radiata (Hymenoptera: Eulophidae) on Flowers and Extrafloral Nectaries: Potential use of Nectar Plants for Conservation Biological Control of Asian Citrus Psyllid (Hemiptera: Liviidae)

Article

Full-text available

Mar 2017

Tamarixia radiata (Waterson) (Hymenoptera: Eulophidae) is a specialist parasitoid of late-instar nymphs of Asian citrus psyllid, Diaphorina citri (Kuwayama) (Hemiptera: Liviidae), a vector of the causal agent of huanglongbing disease of citrus (Sapindales: Rutaceae). Tamarixia radiata is mass reared; however, parasitism levels following inundative releases have remained relatively low. One possible explanation for the low parasitism levels is the lack of sugar resources available for adult wasps in targeted release landscapes, such as abandoned commercial citrus groves and residential areas. Establishing nectar plants can be an effective means of increasing nutritional resources in targeted sites for biocontrol agents. Some eulophids forage effectively only on fully exposed nectaries, i.e., those unobstructed by other floral parts. Therefore, care must be taken to select plants that possess nectary architecture compatible with parasitoid morphology and foraging ability. A series of laboratory studies were undertaken as a first step to determine the potential for T. radiata to obtain sugar from natural sources in target landscapes. Following contact with a sugar spot on filter paper, the wasps engaged in stereotypical zigzagging movements, demonstrating that contact with sugar induced arrestment and induction of localized searching behavior. Tamarixia radiata fed on sugars found in nectar (sucrose, glucose, fructose) and honeydew (melizitose, raffinose), indicating that it should feed well on both nectar and honeydew resources. At the highest concentration tested (1 M), it preferred sucrose and melizitose, whereas at the lowest concentration tested (0.1 M), it preferred sucrose and glucose. There was no preference among sugars when tested at the 0.5 M concentration. Choice tests with wasps previously exposed to scented sucrose solution showed that the wasps were stimulated and attracted by nectar odor and could learn to associate a particular odor with the presence of nectar. Observations conducted with starved wasps on freshly cut sprigs of nectar plants showed that foraging success was highest on extrafloral nectaries and flowers with exposed nectaries. The wasps readily located the extrafloral nectaries on snap bean and cowpea, and fed on them for the majority of the observation periods. Likewise, they quickly located the fully exposed nectaries in the inflorescences of euphorbiaceous plants, such as Euphorbia heterophylla L. (Malpighiales: Euphorbiaceae). Foraging success declined in flowers with nectaries that were only partially exposed; the wasps' movements were deterred by floral parts or trichomes that obstructed the nectary. The wasps were unable to obtain nectar from composites and other plants with hidden nectaries. Overall, the results of these laboratory evaluations showed that T. radiata responds to sugars and chemical cues associated with nectaries and is capable of foraging on extrafloral nectaries and flowers with exposed nectaries.

Floral Strips Attract Beneficial Insects but Do Not Enhance Yield in Cucumber Fields

Article

Feb 2017

Natural enemies and pollinators require nutritional and habitat resources that are often not found in conventional agricultural fields. The addition of flowering plants within agroecosystems may provide the resources necessary to support beneficial insects at the local scale. We hypothesized that insect pollinator and natural enemy abundance would increase in cucumber (Cucumis sativus) plots containing flower strips and that the effect would be greatest in the crop rows closest to the flower strips. Three flower treatments were tested: 1) buckwheat (Fagopyrum esculentum), 2) yellow mustard (Brassica hirta), 3) sweet alyssum (Lobularia maritima), and cucumbers as a control. Flowers were planted within a commercial cucumber field in 20-m-long strips in a randomized complete block design with six replications in the 2014 and 2015 growing seasons. Some floral treatments successfully attracted more beneficial insects than others, but the beneficials did not disperse out to the cucumber plants. Cucumber yield was unaffected by flowers with one exception: in 2015, cucumber yield in the sweet alyssum plots were greater than those in plots with no flowers. Our research indicates that adding flowers to cucumber fields to increase services from beneficial insects needs to be further investigated to better understand the effect of factors such as relative flowering strip size.

The contribution of a beneficial insectary plant Scaevola aemula to survival and long-term establishment of flightless Harmonia axyridis in greenhouses

Article

Jan 2017

The fairy fan flower, Scaevola aemula R. Br., is a primary candidate insectary plant for maintaining populations of generalist predators. We conducted release experiments in greenhouses of cultivated eggplants to evaluate the effects of intercropping S. aemula on the establishment of flightless Harmonia axyridis Pallas. Compared with a monoculture of eggplant, all release experiments showed that flightless H. axyridis remained in greater numbers in plots with S. aemula planted alongside eggplant. In the release experiment of flightless H. axyridis larvae, the incidence of aphids in the plot with transplanted S. aemula was suppressed compared with that in the release plot without transplanted S. aemula. In a laboratory experiment, the longevity of flightless H. axyridis adults on blossom stems of S. aemula was greater than when open flowers and buds were removed, suggesting that the insects fed on floral resources such as the pollen of S. aemula. Our findings showed that the floral resources of S. aemula can enhance aphid suppression by improving the establishment of flightless H. axyridis.

Variety mixtures of wheat influence aphid populations and attract an aphid predator

Article

Full-text available

Apr 2017
ARTHROPOD-PLANT INTE

In crop fields, increasing plant species diversity can help manage insect pests, but using plant intraspecific diversity has received less attention as an insect pest management strategy. To explore the potential of crop genotypic diversity for managing insect pests, we used a wheat-aphid-lady beetle model system. We performed greenhouse and laboratory experiments comparing six monocultures and four-variety mixtures. We found that genotypic diversity did not strongly influence aphid populations at the stand level, but did stabilize populations. At the individual plant level, populations on certain varieties differed in mixtures from what would be expected based on populations on the variety in monocultures, including one that consistently hosted lower aphid populations when it was grown in mixtures. When we then tested five of the most promising mixtures, we found none decreased aphid populations compared to monocultures. Diversity of the surrounding neighborhood significantly influenced aphid populations on individual plants of certain varieties. Wheat mixtures did not overyield relative to monocultures, as other studies have found, but all measures of productivity were stabilized by mixtures. In behavioral experiments, aphids did not prefer mixtures or monocultures, but lady beetles were significantly attracted to mixtures. In the field, bottom-up effects on aphids and effects on natural enemies could create pest-management benefits. Based on the work we present here, increasing diversity per se may not improve aphid management aside from stabilizing populations; rather, specific types of mixtures that include influential varieties appear to be crucial for fostering beneficial interactions that can benefit insect pest management.

Ökonomische Analyse des Einsatzes von Pflanzenschutzmitteln – Risikoaspekte und Lenkungsabgaben

Technical Report

Full-text available

Oct 2016

Pflanzenschutz ist essentiell, um die Bereitstellung qualitativ hochwertiger Lebensmittel in ausreichender Quantität zu gewährleisten. Insbesondere der Einsatz von Pflanzenschutzmitteln (PSM) geht dabei jedoch oft auch mit möglichen negativen Effekten für die Umwelt und menschliche Gesundheit einher. Aufgrund dessen ist die Reduktion der mit dem Einsatz von PSM verbundenen negativen Effekte ein wichtiges Ziel der Schweizer Agrar- und Umweltpolitik. Der im Juli 2016 veröffentlichte Entwurf für den „Aktionsplan zur Risikoreduktion und nachhaltigen Anwendung von Pflanzenschutzmitteln“ postuliert das Ziel, die durch den Einsatz von PSM hervorgerufenen Risiken um 50% zu reduzieren. Dieses Ziel soll mit einer Kombination von verschiedenen Massnahmen erreicht werden, welche unter anderem die Anwendungen und Emissionen von PSM reduzieren. Begleitende Instrumente und Massnahmen, beispielsweise aus dem Bereich Beratung und Ausbildung, sollen zur Erreichung dieses Ziels beitragen. In diesem Kontext ist es das Ziel dieser Studie, zu einem besseren Verständnis der ökonomischen Wirkung von möglichen Lenkungsmechanismen des PSM-Einsatzes in der Schweizer Landwirtschaft beizutragen. Dabei wurde im Auftrag des Bundesamts für Landwirtschaft untersucht: - Welche Wirkung eine Lenkungsabgabe auf den Einsatz und die Risiken von PSM haben könnte; - Welches Design einer Lenkungsabgabe dabei die agrarpolitischen Zielvorgaben am besten erfüllen kann; - Inwiefern Versicherungen eine sinnvolle Begleitmassnahme darstellen, die den PSM-Einsatz reduzieren können; und - Welche ökonomischen Effekte durch eine Abgabe auf PSM induziert werden würden, und wie negative Auswirkungen aufgefangen werden können? Zur Beantwortung dieser Forschungsfragen wurde eine Kombination verschiedener methodischer Ansätze verwendet, welche qualitative und quantitative Analysen der bestehenden Literatur als auch spezifische theoretische und empirische Analysen für die schweizerische Landwirtschaft umfassen. Für detaillierte Darstellungen des methodischen Vorgehens und der Ergebnisse sei auf den Bericht verwiesen. Die Folgerungen aus den in dieser Studie durchgeführten Analysen können in sechs Kernpunkten zusammengefasst werden: (1) Differenzierte PSM-Abgabensysteme können die durch den Einsatz von PSM hervorgerufenen Risiken für Mensch und Umwelt effektiv reduzieren. Dabei sollten nur sehr risikoreiche Produkte stark besteuert werden, wodurch eine Substitution zu weniger risikoreichen Produkten und nicht-chemischen Pflanzenschutzstrategien angeregt wird und die durchschnittliche Abgabenlast gering gehalten werden kann. Im Gegensatz zu Verboten von PSM, wird das Spektrum der möglichen Pflanzenschutzstrategien dabei nicht verkleinert. Die Aufhebung der Steuersubventionierung von PSM in der Schweiz ist dabei ein notwendiger erster Schritt. (2) Die Erhebung der Abgabe auf Ebene Handel oder Industrie sowie die Nutzung der im PSM-Zulassungsverfahren generierten Informationen führen zu tiefen Transaktionskosten bei der Einführung von Lenkungsabgaben auf PSM. (3) Die zwar vorhandene, aber nicht sehr grosse Elastizität der Nachfrage nach PSM impliziert, dass die Abgaben für risikoreiche Produkte sehr hoch sein müssten, um relevante Mengenreduktionen zu realisieren. (4) Eine Rückvergütung der Erlöse aus einer Abgabe in den Sektor trägt zur Vermeidung von Einkommensverlusten bei. Geschieht diese Rückvergütung mittels Instrumenten, die das Risiko des PSM-Einsatzes weiter reduzieren, können wichtige Hebelwirkungen kreiert werden. Diese Rückvergütung sollte sich auf Ansätze fokussieren, die keine Reduktion der Produktionsmengen implizieren (z.B. für bessere Ausbringungstechnik, Verbesserung nicht-chemischen Pflanzenschutzes), um so Leakage-Effekten, also der Substitution wenig PSM-intensiver (heimischer) Produkte durch PSM-intensive (importierte) Produkte, vorzubeugen. Die Nutzung einer Lenkungsabgabe ist nur als Bestandteil eines kohärenten Massnahmenpakets sinnvoll. Dies ist von spezifischer Bedeutung in intensiven Produktionssystemen mit geringen Nachfragelastizitäten für PSM. (5) Eine PSM-Lenkungsabgabe hat kurzfristig nur geringe Effekte, setzt aber Anreize für mittel- und langfristige Entwicklungen zur nachhaltigen Reduktion der durch den PSM-Einsatz hervorgerufenen Risiken. (6) Eine Subventionierung von Ertrags- oder Erlösversicherung führt nicht notwendigerweise zu einer Reduktion des PSM-Einsatzes, auch wenn damit andere Politikziele erreicht werden können. Andere Begleitmassnahmen sind hinsichtlich der Reduktion der durch den Einsatz von PSM hervorgerufenen Risiken zielführender. Basierend auf diesen Erkenntnissen kann festgehalten werden, dass eine richtig ausgestaltete Lenkungsabgabe einen Beitrag dazu leisten kann, die im Aktionsplan postulierten agrar- und umweltpolitischen Ziele zu erreichen. Die Abgabe kann jedoch nur ein Instrument im Rahmen eines kohärenten Sets von sich ergänzenden Massnahmen sein. In Bezug auf die konkrete Ausgestaltung des Instruments, deren Einbindung in den Aktionsplan und die ökonomischen Auswirkungen auf den Sektor sind weitere Analysen angezeigt.

A Field Survey of Syrphid Species and Adult Densities on Annual Flowering Plants in the Northeastern United States

Article

Feb 2023
ENVIRON ENTOMOL

With the long-term goal of exploring the viability of conservation biological control of cabbage aphid Brevicoryne brassicae (L.) (Hemiptera: Aphididae) in the northeastern United States, adult syrphid flies (Diptera: Syrphidae) were observed on several species of annual insectary plants at farm sites in Connecticut, Massachusetts, and New Hampshire. Insectary plant species included alyssum, Lobularia maritima (L.) (Brassicales: Brassicaceae), buckwheat, Fagopyrum esculentum (Moench) (Caryophyllales: Polygonaceae), phacelia, Phacelia tanacetifolia (Bentham) (Boraginales: Hydrophyllaceae), calendula, Calendula officinalis (L.) (Asterales: Asteraceae) and ammi, Ammi majus (L.) (Apiales: Apiaceae). Among these insectary plants, alyssum had the longest bloom period and attracted the most syrphids. We identified 21 species of syrphid flies from insectary plants. The three most prevalent species collected were the aphidophagous Toxomerus marginatus (Say) (Diptera: Syrphidae) (70.1% of samples) and T. geminatus (Say) (Diptera: Syrphidae) (8.8% of samples), as well as the non-aphidophagous Syritta pipiens (L.) (Diptera: Syrphidae) (13.1% of samples). The benefits of including these insectary plant species as a companion to Brassica (L.) (Brassicales: Brassicaceae) cropping systems are discussed.

Impact de l'arrangement spatial des cultures associées sur la distribution des ressources trophiques pour les parasitoïdes et le contrôle biologique des pucerons

Thesis

Full-text available

Jun 2022

Louise Lérault

La distribution hétérogène des ressources trophiques dans l’environnement des organismes influence leurs patrons d’exploitation.Les agroécosystèmes ont une structuration spatiale marquée des ressources trophiques essentielles aux parasitoïdes, à savoir les hôtes et la nourriture sucrée.L’association d’une culture non productrice de nectar avec une culture nectarifère est un modèle intéressant pour étudier l’influence de l’apport de ressources trophiques au sein des parcelles,et pourrait favoriser le service écosystémique de régulation des ravageurs par les parasitoïdes. Ces cultures associées peuvent être agencées selon différents arrangements spatiaux, qui font varier la distribution spatiale des ressources.Dans la cadre de cette thèse, nous explorons l’influence de la distribution spatiale des ressources trophiques dans les cultures associées sur le comportement alimentaire des parasitoïdes et le parasitisme des pucerons.Dans un premier temps, nous étudions l’influence de la distance entre hôtes et nectar sur l’alimentation et le parasitisme de femelles Aphidius ervi. Nous observons que la présence d’hôtes influence la fréquence d’alimentation mais pas le taux de parasitisme. Dans un second temps, nous explorons la complémentarité potentielle entre l’apport d’hôtes alternatifs et de nectar et la portée spatiale de cet aménagement en inter-rang en verger. Nous n’observons pas d’effet de l’apport de chaque ressource ni de la combinaison des deux sur le parasitisme des pucerons. Enfin, nous étudions l’effet du mode d’arrangement spatial d’une association céréale-légumineuse, et le comparons avec une culture pure de céréale. Nous observons un effet opposé de l’association culturale sur les populations de pucerons selon la culture, avec moins de pucerons en association sur la légumineuse et plus sur la céréale dans les arrangements fins, mais sans lien avec l’activité des parasitoïdes. Nos résultats ne permettent pas de confirmer l’effet bénéfique des cultures associées sur le contrôle biologique des pucerons par les parasitoïdes. Déterminer les conditions environnementales de disponibilité de ressources dans lesquelles l’apport de nectar pourrait avoir un impact et la portée spatiale d’aménagement à une échelle plus large, permettrait peut-être d’expliquer cette absence d’effet de l’approvisionnement en ressources trophiques pour les parasitoïdes.

Organic Horticulture

Article

Jan 2022

M Dorais

This datasheet on Organic Horticulture covers Identity, Overview, Description, Further Information.

Does intercropping patterns of potato and safflower affect the density of Leptinotarsa decemlineata (Say), predators, and the yield of crops?

Article

Sep 2022
BIOL CONTROL

The impact of three intercrop patterns of potato (P), Solanum tuberosum L., and safflower (S), Carthamus tinctorius L.: 4P:2S, 4P:4S, and 4P:8S (row ratios) along with single crops were examined on densities of the Colorado potato beetle (CPB), Leptinotarsa decemlineata (Say), biodiversity of predators, and yield profits over the growing season of potatoes in a randomized complete block design in 2019 and 2020 in Iran. The significant reduction in the densities of CPB (adults, eggs, and larvae) was seen in intercrops compared with single potato in either year. Accordingly, the damage index was decreased in intercrops than in single potato. Furthermore, intercrops resulted in an enhancement in the abundance of most predatory species of CPB, the Shannon diversity index (H΄), and the Pielou's evenness index (J'), especially in 4P:4S and 4P:8S than single potato. The values of R² between the densities of CPB and the main predators were low (0.01 ≤ R² ≤ 0.19) in June, whereas R² values were significantly enhanced in July (0.13 ≤ R² ≤ 0.71) and August (0.46 ≤ R² ≤ 0.97). All intercrops delivered extra yield benefit compared with the single crops (LER ≥ 1.20 in 2019 and ≥ 1.18 in 2020). Our results disclosed that all intercrops, especially 4P:4S and 4P:8S could exercise in the controlling of L. decemlineata in potato fields.

Can the introduction of companion plants increase biological control services of key pests in organic squash?

Article

Jan 2022

Florida (USA) is a major producer of squash, Cucurbita pepo L. (Cucurbitaceae), with approximated 16% of the US production in 2019, valued at about 35 million USD. Major insect pests, including the sweetpotato whitefly MEAM1, Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae), and the melon aphid, Aphis gossypii Glover (Hemiptera: Aphididae), jeopardize plant development and transmit viruses of economic importance that can cause up to 50% yield loss in squash crops. Pesticides are generally used for insect management in squash, but the development of insecticide resistance and their non-target effects are major concerns. A combination of non-pesticidal approaches was evaluated, including intercropping flowering plants, augmentation, and conservation biological control to manage key pests in organic squash. Refugia increased natural enemies around the squash; however, only a few beneficial arthropods moved from the companion plants towards the squash plants. Whitefly densities and squash silverleaf ratings were reduced, whereas natural enemies were more abundant when the predatory mite Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae) was released alone or together with sweet alyssum, Lobularia maritima (L.) Desv. (Brassicaceae). All companion plants used in this study increased natural enemies, but only African marigolds and sweet alyssum ultimately increased biological control activities.

Challenges and Opportunities in Managing Pests in No-Till Farming Systems

Chapter

Sep 2020

Ebony G Murrell

Tillage has both positive and negative effects on pest management in agriculture, depending on the pest being managed. This chapter discusses the pros and cons of no-till (NT) systems in regard to pest pressure. The success and environmental sustainability of pest management in NT systems depends on the agricultural methods that are used in tandem with the cessation of tillage. Insecticides are often used in NT systems, meaning that pesticide runoff from fields and damage to nontarget insect species remain as much, if not more, concerning in NT agriculture versus conventional tillage (CT) systems. Crop rotation, use of pest-resistant crop varieties, manipulation of planting and harvest dates, retention of crop residues, and intercropping are alternative practices that are fully integrative with NT systems. These practices, when paired with NT agriculture, can promote soil microbiota that improve plant defenses, encourage colonization of beneficial predators and parasitoids, and reduce pest abundances and the need for insecticide treatments in NT fields.

Measuring the effect of non-crop flowering plants on natural enemies in organic tobacco

Article

Jul 2019

The use of “insectary strips” of sunflowers and buckwheat is widely promoted by organic certifiers to promote control of the green peach aphid (Myzus persicae) and other pests in organic tobacco. However, no published research supports this recommendation in tobacco, and results from other crops are mixed. We performed a series of experiments to test the effects of non-crop plantings of sunflowers and buckwheat on key pest and beneficial insects adjacent to organic tobacco fields in North Carolina. Although some reduction in M. persicae infestations and increases in numbers of beneficial insects were observed on tobacco plants near field-edge insectary treatments, these effects were small and were observed only over a short distance into the crop. Planting additional insectary strips in the field interior did not reduce aphid numbers in comparison to control treatments and led to increases in some pest insects. These conservation biological control techniques are unlikely to be a reliable method of controlling M. persicae and other pest insects in organic tobacco.

Can buffers of partridge pea (Chamaecrista fasciculata)enhance beneficial arthropod communities in neighboring soybeans?

Article

Sep 2018

Grass buffer strips are often deployed along crop borders as part of conservation programs to improve water quality, filter sediments from runoff, and foster wildlife biodiversity. Addition of wildflowers in these strips can augment natural enemies by provisioning nectar and pollen resources. Here we investigated the impact of partridge pea [Chamaecrista fasciculata (Michx.) Greene] as an insectary plant to enhance natural enemy abundance in adjacent soybeans. In 2005, sticky card counts of hymenopteran and dipteran parasitoids were 72.7% higher in buffers of partridge pea and partridge pea mixed with purple tansy (Phacelia tanacetifolia Benth.) compared to purple tansy grown alone or proso millet (Panicum miliaceum L.), whereas predator abundance was greater in purple tansy and millet compared to buffers with partridge pea. Similarly, communities of beneficial arthropods captured in 2006 by sticky card and pitfall traps were 79.8 to 72.3% higher, respectively, in partridge pea buffers compared to neighboring soybeans. Buffer effects on populations of parasitoids and predators in adjoining soybean fields were mixed and varied among taxon groups. Partridge pea was a source for dipteran parasitoids and saprovores, but density effects were generally not discernible beyond 6 m within the adjoining soybean. More significantly, partridge pea acted as a natural enemy sink for mymarid parasitoids, dipteran predators, and ground-dwelling ants, and had a neutral effect on other arthropod guilds. Implications of these findings are discussed.

Ảnh hưởng các nguồn thức ăn từ hoa đến tuổi thọ và khả năng ký sinh của ong ký sinh Cotesia vestalis (Haliday) (Hymenoptera:Braconidae)

Article

Full-text available

Jan 2018

Bibliography

Chapter

Jul 2018

Alyssum flowers promote biological control of collard pests

Article

Jan 2017

Collard greens Brassica oleracea (L.) are often attacked by various pests including whiteflies, aphids and diamondback moth. Hitherto, the main method used to manage these pests in Brazil has been the application of a limited number of registered insecticides. The search for more sustainable pest management strategies is therefore warranted. In this context, the conservation biological control stands out as an appealing alternative. Conservation biological control is achieved, at least in part, by strip-cultivating and/or conserving flowering plants within the agroecosystem. The present study investigates how alyssum flowers Lobularia maritima (L.) could contribute to the attraction of natural enemies and to the management of collard pests. Two field experiments were conducted in different years. Each experiment consisted of two treatments and three replicates, which were set up in a completely randomized design. The treatments were (1) collards alone, and (2) collards + alyssum. We evaluated weekly the population density of natural enemies and pests on both treatments. The results show that the alyssum flowers attractiveness contributed to increase the abundance of generalist predators during both experiments, which in turn translated into a significant reduction of collards pests, especially aphids. Some of the main predators attracted/harbored by alyssum flowers were spiders, coccinellids, syrphids and Orius sp. Finally, strip intercropping alyssum with collards can be an important strategy to manage brassica pests and cope with the limited availability of insecticides registered for this vegetable crop.

The behaviour of hoverfly larvae (Diptera, Syrphidae) lessens the effect of floral subsidy in agricultural landscapes

Article

Full-text available

Mar 2016

Modern agricultural landscapes favour crop pests: herbivores benefit from resource concentration and/or the absence of natural enemies in large areas of intensively farmed fields interspersed by small fragments of natural or non-crop habitats. Conservation biological control (CBC) aims at increasing the functional diversity of agricultural landscapes to make them more hospitable to natural enemies, and less to herbivores. Although natural enemies readily respond to this management, very few studies assess if they succeed in effectively protecting crops. We set up a field experiment to study if an ecological infrastructure varying in size and consisting of the provision of floral resources at the centre of lettuce plots would influence the number of eggs laid by hoverflies, and ultimately the control of lettuce aphids. We found that the hoverfly females lay more eggs in the plots with the larger flower resource compared to the control. However, this response had no impact on the abundance of aphids on the lettuces. We designed two laboratory experiments to understand this absence of response. We found mutual interference between hoverfly larvae, and suggest it may undermine the biological control of aphids. This mismatch between landscape management and the response of hoverflies indicates CBC should take into account insect behaviour, particularly their response to conspecific density, additionally to landscape ecology.

Resistance to Lettuce Aphid (Nasonovia ribisnigri) Biotype 0 in Wild Lettuce Accessions PI 491093 and PI 274378

Article

Full-text available

Feb 2012
HORTSCIENCE

The lettuce aphid, Nasonovia ribisnigri Mosley (Hemiptera: Aphididae), is a major insect pest of lettuce, Lactuca sativa L, in many commercial lettuce production areas around the world. Resistance to lettuce aphid biotype 0 (Nr:0) was first reported in Lactuca virosa L. accession IVT 280 and characterized as complete, i.e., virtually no aphids survived, and genetically dominant to partial resistance in L. virosa accession IVT 273. Complete and partial resistances to Nr:0 were conditioned by two alleles, Nr (complete resistance) and nr (partial resistance), but the genetic relationship to susceptibility was not reported. We previously reported two new potential sources of unique genes for resistance to Nr:0 in Lactuca serriola L. accession PI 491093 and L. virosa PI 274378. We report on the genetic and phenotypic nature of resistance to Nr:0 in these two wild lettuce accessions. Resistance to Nr:0 in PI 274378 is complete and allelic to complete resistance in IVT 280. Resistance to Nr:0 in PI 491093 was partial, recessive to complete resistance in 'Barcelona' that was derived from IVT 280, but dominant to susceptibility in 'Salinas'. We propose the revised gene symbols for resistance to Nr:0: Nr:0C for complete resistance and Nr:0P for partial resistance, which was originally designated as nr but may now be regarded as the symbol for susceptibility to all strains of lettuce aphid. The dominance relationships among these three alleles are Nr:0C (in IVT 280, 'Barcelona') > Nr:0P (in PI 491093) > nr (in susceptible genotypes). Expression of partial resistance in PI 491093 was variable in controlled infestation tests, but in a naturally infested field test provided a potentially useful level of resistance to Nr:0. Partial resistance, where complete resistance has not been widely deployed, may either alone or as a component of integrated pest management delay or prevent emergence of genotypes that overcome complete resistance controlled by Nr:0C.

Flower Flies (Syrphidae) and Other Biological Control Agents for Aphids in Vegetable Crops

Article

Full-text available

Jan 2008

Winter Cover Crop Seeding Rate and Variety Affects during Eight Years of Organic Vegetables: I.Cover Crop Biomass Production

Article

Full-text available

May 2012

Long-term research on cover crops (CC) is needed to design optimal rotations. Winter CC shoot dry matter (DM) of rye (Secale cereale L.), legume-rye, and mustard was determined in December to February or March during the first 8 yr of the Salinas Organic Cropping Systems trial focused on high-value crops in Salinas, CA. By seed weight, legume-rye included 10% rye, 35% faba (Vicia faba L.), 25% pea (Pisum sativum L.), and 15% each of common vetch (V sativa L.) and purple vetch (V. henghalensis L.); mustard included 61% Sinapis alba L. and 39% Brassica juncea Czern. Cover crops were fall-planted at 1x and 3x seeding rates (SR); 1x SR were 90 (rye), 11 (mustard), and 140 (legume-rye) kg ha(-1). Vegetables followed CC annually. Cover crop densities ranged from 131 to 854 plants m(-2) and varied by CC, SR, and year. Year, CC, and SR affected DM production, however, the effects varied across the season and interactions occurred. Averaged across years, final DM was greater in rye and legume-rye (7 Mg ha(-1)) than mustard (5.6 Mg ha(-1)), and increased with SR through January. Dry matter production through the season was correlated significantly with growing degree days (GDD). Legumes contributed 27% of final legume-rye DM. Season-end legume DM was negatively correlated with GDD at 30 d, and legume DM in the 3x SR increased during years with frequent late-season rainfall. Seed costs per Mg of final CC DM at 1x SR were approximately three times higher for legume-rye than rye and mustard.

The role of omnivory in the conservation of predators: Orius majusculus (Heteroptera: Anthocoridae) on sweet alyssum

Article

Full-text available

Jul 2012

In conservation biological control programs, provision of the required resources (shelter, food, oviposition sites) can be achieved by means of the use of insectary plants. This is especially important in the case of omnivorous predators that feed on prey and plant materials, and where the availability of plant resources plays a significant role in their conservation. An important predator of thrips and other pests in the Mediterranean is the omnivorous bug Orius majusculus (Reuter) (Hemiptera: Anthocoridae). The objective of this study was to evaluate the fertility, fecundity and longevity of O. majusculus on alyssum, (Lobularia maritima L.) with and without prey (Ephestia kuehniella eggs), and compare it with green bean pods. Additionally, the effects of the breeding colony of the individuals on the fertility of O. majusculus were studied. Fecundity on both plants without prey was low; however the addition of prey significantly increased the number of eggs laid, especially on alyssum. The longevity differed significantly among diets, being longer for alyssum with prey eggs. Survival on alyssum without prey was not statistically different from green bean with prey, which shows the potential of alyssum to conserve O. majusculus during times of prey scarcity. The fertility of O. majusculus females was significantly higher on the diets of both plant materials when prey was included. Our results showed that alyssum can provide resource subsidies for O. majusculus during times of prey scarcity in the field.

Secondary plants used in biological control: A review

Article

Full-text available

Apr 2012

In crop systems, different types of plant or secondary crop may be grown together with the primary crop for pest management purposes. These additional plants – henceforth called secondary plants – may increase the efficiency and sustainability of biological control of pests by natural enemies. Such plants fall into several categories; companion, repellent, barrier, indicator, trap, insectary, and banker. Despite their effectiveness and accepted function in biological control, to date the full potential of secondary plants in integrated pest management has not been put to good use. This may be partly attributed to a lack of detailed knowledge of the way the secondary plant-crop systems operate, including the effects of the secondary plants on tritrophic interactions. The biggest constraint upon progress, however, has been confusion over definitions and terminology. In this paper, we review the knowledge of the currently employed plant categories and provide clear definitions.

Growth, development and consumption by four syrphid species associated with the lettuce aphid, Nasonovia ribisnigri, in California

Article

Full-text available

Sep 2011

The lettuce aphid, Nasonovia ribisnigri Mosley, was accidentally introduced into California from Europe during the late 1990s and soon became an economic pest of Romaine lettuce along California’s central coast region. Indigenous syrphid larvae attack the lettuce aphid and are believed to be effective in the management of this invasive pest, although there have been no studies on the capacity of the syrphid larvae to kill and consume lettuce aphids. We focused on four syrphid species commonly found in central coast lettuce fields: Allograpta obliqua (Say), Eupeodes fumipennis (Thomson), Sphaerophoria sulphuripes (Thomson), and Toxomerus marginatus (Say). Laboratory feeding experiments were conducted to estimate the development times of all juvenile stages, the daily growth rate of larvae, the number of third instar aphids killed, the aphid biomass killed, and the aphid biomass consumed as measures of predator performance. Results show that during larval development E. fumipennis killed the most third-instar aphids (507 aphids, 88mg biomass killed) and reached the largest size, followed by A. obliqua (228 aphids, 39mg killed), S. sulphuripes (194 aphids, 31mg killed) and T. marginatus (132 aphids, 20mg killed). Body size alone did not account for species differences in per-capita larval consumption rates. This information is discussed in relation to the predation potential of syrphids through the short cropping cycle of lettuce, and the choice of plant species to use for floral resource provisioning to enhance the activity of syrphids needed for effective management of lettuce aphids in California’s central coast fields.

Relative Frequencies of Visits to Selected Insectary Plants by Predatory Hoverflies (Diptera: Syrphidae), Other Beneficial Insects, and Herbivores

Article

Full-text available

Apr 2006
ENVIRON ENTOMOL

The use of insectary plants in agroecosystems to provide floral resources for enhancing natural enemy activity is an increasingly used practice, but candidate flowering plant species are not always screened for their attractiveness to key arthropods in the system being studied. In the work presented here, the relative attractiveness of four species of insectary plants to beneficial and pest insect species was assessed by observing the relative frequencies of flower visits to replicated blocks of the insectary flowers in two Oregon broccoli fields. The four plant species tested were alyssum (Lobularia maritima L. Desv.), coriander (Coriandrum sativa L.), buckwheat (Fagopyrum esculentum Moench), and phacelia (Phacelia tanacetifolia Benth.). Predatory hoverflies (Syrphidae) were identified to species, where possible, because of their previously observed importance as aphid predators in broccoli fields in the study area. The other beneficial insect groups observed were in the families Apidae, Coccinellidae, Tachinidae, and Vespidae, and the three main pest species were western tarnished plant bug (Lygus hesperus Knight), western spotted cucumber beetle (Diabrotica undecimpunctata undecimpunctata Mannerheim), and imported cabbageworm (Pieris rapae L.). The Syrphidae visited mostly coriander, but this “preference” was probably influenced by competition from other foragers. Bumblebees and the three pest species visited mostly phacelia, and other species groups were less consistent in their flower choices. The different insect preferences for flowers are discussed in terms of the key influencing factors that should be considered when assessing the relative attractiveness of insectary plants in the field.

Floral resources enhance aphid suppression by a hoverfly

Article

Full-text available

Oct 2011
ENTOMOL EXP APPL

The reduction in floral diversity that often accompanies agricultural intensification may compromise the effectiveness of many natural enemies. Field studies examining the effects of floral resources on natural enemy fitness have been rare, however, particularly for predators such as hoverflies. Making the link between the presence of floral resources and the suppression of herbivores in crop fields has proved difficult. We investigated the effects of the floral resource plant sweet alyssum, Lobularia maritima (L.) Desv. (Brassicaceae), on aphid suppression by the hoverfly Eupeodes fumipennis (Thomson) (Diptera: Syrphidae) in California lettuce fields. The presence of alyssum in field cages significantly enhanced hoverfly egg production, resulting in more hoverfly larvae and fewer aphids (Hemiptera: Aphididae). Hoverfly survival was unaffected by alyssum, indicating that the indirect effect of alyssum on aphids was mediated primarily through the reproductive component of hoverfly fitness. Alyssum and other plant species are used to enhance resources for natural enemies in agricultural landscapes, and the results of this study provide some of the clearest evidence to date that increasing floral resource availability can enhance pest suppression and crop quality through elevated natural enemy fitness.

Attractiveness of common insectary and harvestable floral resources to hoverflies

Article

Full-text available

Jan 2011
BIOL CONTROL

Resources for natural enemies are often lacking in agricultural fields. The provisioning of floral resources in crop fields can ameliorate this problem by providing nectar and pollen to natural enemies. To select an appropriate floral resource, plants must be screened for their flowering times and attractiveness to natural enemies and pests. We tested the attractiveness of nine species of annual flowering plants to hoverflies, which are important predators of aphids in California lettuce fields. We also sampled arthropods in the foliage of tested plants, to assess the abundances of other natural enemy and pest species that were present. Tested plants included three commonly-used insectary plants and six flowering plant species that showed potential as either harvestable herbs or cut flowers. Harvestable insectary plants may provide additional economic incentive for growers to set aside land for floral resources. The commonly-used insectary plant sweet alyssum consistently attracted the most hoverflies and the least bees, while potentially harvestable plants attracted few hoverflies. Competition with bees may have reduced hoverfly visits to several of the tested plant species. Sweet alyssum also stayed in bloom the longest, and contained the highest numbers of predatory hemipterans. Results suggest that plants should be screened for their attractiveness to not only the target biological control agent, but also to other potential competitors for floral resources. While this initial study focused on a limited selection of harvestable annual plants, a wide variety of other marketable plant species, particularly perennials, remain to be tested for their attractiveness to hoverflies or other beneficial arthropods.

Habitat Management to Conserve Natural Enemies of Arthropod Pests in Agriculture

Article

Full-text available

Feb 2000

Many agroecosystems are unfavorable environments for natural enemies due to high levels of disturbance. Habitat management, a form of conservation biological control, is an ecologically based approach aimed at favoring natural enemies and enhancing biological control in agricultural systems. The goal of habitat management is to create a suitable ecological infrastructure within the agricultural landscape to provide resources such as food for adult natural enemies, alternative prey or hosts, and shelter from adverse conditions. These resources must be integrated into the landscape in a way that is spatially and temporally favorable to natural enemies and practical for producers to implement. The rapidly expanding literature on habitat management is reviewed with attention to practices for favoring predators and parasitoids, implementation of habitat management, and the contributions of modeling and ecological theory to this developing area of conservation biological control. The potential to integrate the goals of habitat management for natural enemies and nature conservation is discussed.

Distribution and Population Development of Nasonovia ribisnigri (Homoptera: Aphididae) in Iceberg Lettuce

Article

Full-text available

Jul 2004
J ECON ENTOMOL

Yong-Biao Liu

A field study was conducted to determine the distribution and development of aphid Nasonovia ribisnigri (Mosley) (Homoptera: Aphididae) populations in iceberg lettuce, Lactuca sativa L. 'Salinas'. Lettuce plants were transplanted and caged individually in the field and inoculated with apterous N. ribisnigri at 0, 1, 2, 3, and 4 wk after transplanting in spring and fall 2002. Plants were harvested 15-50 d after inoculations; numbers of alates and apterous N. ribisnigri were counted or estimated on each leaf for each plant. Inoculations during all 5 wk of plant development resulted in successful colonization of lettuce heads. Results indicated that head formation did not reduce the risk of colonization by N. ribisnigri to iceberg lettuce; plants were susceptible to colonization by N. ribisnigri throughout their development. For later inoculations, N. ribisnigri populations were relatively smaller, and aphids were found mostly within the heads. For earlier inoculations, N. ribisnigri populations were larger, and within-plant distributions shifted toward frame leaves. The shift of population distributions toward frame leaves correlated significantly with increases in N. ribisnigri population density. For most inoculations, more aphids were present on wrapper leaves than on other leaves. The proportion of alates did not vary significantly with population density. Population development of N ribisnigri also correlated significantly with heat unit accumulation. Yellow sticky cards were used to monitor alates in each cage. Catches of N. ribisnigri alates on yellow sticky cards were significantly correlated with total numbers of alates as well as with total population sizes on individual lettuce plants.

Presidedress Soil Nitrate Testing Reduces Nitrogen Fertilizer Use and Nitrate Leaching Hazard in Lettuce Production

Article

Dec 2002
HORTSCIENCE

Trials were conducted in 15 commercial fields in the central coast region of California in 1999 and 2000 to evaluate the use of presidedress soil nitrate testing (PSNT) to determine sidedress N requirements for production of iceberg and romaine lettuce (Lactuca sativa L.). In each field a large plot (0.2-1.2 ha) was established in which sidedress N application was based on presidedress soil NO3-N concentration. Prior to each sidedress N application scheduled by the cooperating growers, a composite soil sample (top 30 cm) was collected and analyzed for NO3-N. No fertilizer was applied in the PSNT plot at that sidedressing if NO3-N was >20 mg.kg-1; if NO3-N was lower than that threshold, only enough N was applied to increase soil available N to ≈20 mg.kg-1. The productivity and N status of PSNT plots were compared to adjacent plots receiving the growers' standard N fertilization. Cooperating growers applied a seasonal average of 257 kg.ha-1 N, including one to three sidedressings containing 194 kg.ha-1 N. Sidedressing based on PSNT decreased total seasonal and sidedress N application by an average of 43% and 57%, respectively. The majority of the N savings achieved with PSNT occurred at the first sidedressing. There was no significant difference between PSNT and grower N management across fields in lettuce yield or postharvest quality, and only small differences in crop N uptake. At harvest, PSNT plots had on average 8 mg.kg-1 lower residual NO3-N in the top 90 cm of soil than the grower fertilization rate plots, indicating a substantial reduction in subsequent NO3-N leaching hazard. We conclude that PSNT is a reliable management tool that can substantially reduce unnecessary N fertilization in lettuce production.

Surveys on visitation of flowering landscape plants by common biological control agents in Colorado

Article

Apr 1999
J KANSAS ENTOMOL SOC

A study was made to identify flowering landscape plants that are adapted to culture along the northern Front Range of Colorado and that are visited by arthropods important in biological control of plant pests. Periodic surveys were made of regional botanic gardens during 1993 and 1994, during which time over 150 plant species/cultivars in 37 families were assessed for intensity of visitation by various natural enemies of insect pests (Coccinellidae, Chrysopidae, Syrphidae, Braconidae, Sphecidae, Tachinidae). Among the plants found to be visited most frequently were Achillea spp., Anthemis tinctoria 'Kelwayi', Aster alpinus, and Solidago virgaurea 'Peter Pan' (Asteraceae); Anethum graveolens, Astrantia major 'Margery Fish', Coriandrum sativum and Foeniculum vulgare (Apiaceae); Lobularia maritima and Aurinia saxatilis (Brassicaceae); Linaria vulgaris, Penstemon strictus, Veronica spicata 'Blue Fox' and 'Red Fox' (Scrophulariaceae); Ajuga reptans 'Bronze Beauty', Lavandula angustifolia, Mentha x piperita, and Stachys officinalis (Lamiaceae); Sedum album, S. kamtschaticum, and S. spurium 'Dragon's Blood' (Crassulaceae). It is suggested that these plants may be particularly appropriate selections to be used to increase presence and enhance efficacy of natural enemies in regional gardens and landscape plantings by serving as alternate food sources for adult stages.

Biological control of aphids in lettuce using in-field insectaries

Article

Jan 1998

W.E. Chaney

Intercropping: its Importance and Research Needs. Part 2, Agronomy and Research Approaches

Article

Jan 1979

R.W. Willey

Beitrag zur Kenntnis der Generationsverh??ltnisse und Diapause r??uberischer Schwebfliegen (Syrphidae, Dipt.)

Article

F. Schneider

Manipulating floral resources dispersion for hoverflies (Diptera: Syrphidae) in a California lettuce agro-ecosystem

Article

Nov 2011

Conservation biological control as a low-input method of pest management is unlikely to be universally adopted until easily deployable protocols are developed and targeted at farmers. However, critical questions remain concerning maximizing the efficacy of these pest management methods. For example, managing the currant–lettuce aphid on Californian organic lettuce farms currently relies on the presence of hoverfly species with aphidophagous larvae. Although floral resources are planted by the grower to provide food for adult hoverflies, little is known about how much and where floral resources should be provided. In this study, such a grower-initiated field design that is not based on published research is tested. The strips of sweet alyssum planted by the grower at 48m intervals within organic romaine lettuce fields were covered with agricultural frost cover to effectively double the distance between floral strips. Data collection, including egg, larvae and aphid counts, visual censuses of adult flies as well as pan trapping, were conducted before, during and after the application of the covers to establish the effect of changing the dispersion of floral resources. While the period of the row-cover manipulation was too short to establish an effect on egg, aphid and larval numbers, visual counts of adult hoverflies suggested that they reacted rapidly to the change in the local environment when the covers were applied and when they were removed. However, there was evidence to suggest that despite apparent aggregation in visual counts, hoverflies uniformly dispersed throughout the crop, regardless of the presence of covers, suggesting that floral resource provision could be reduced in this system.

Suitability of some farmscaping plants as nectar sources for the parasitoid wasp, Microplitis croceipes (Hymenoptera: Braconidae): Effects on longevity and body nutrients

Article

Mar 2011

In support of an ongoing study to evaluate potential farmscaping plants for utilization in organic vegetable production systems, we examined the effects of the nectar of three flowering plant species, sweet alyssum (Lobularia maritima), buckwheat (Fagopyrum sagittatum), and licorice mint (Agastache foeniculum), on the lifespan and body nutrient levels of the wasp, Microplitis croceipes (Cresson) (Hymenoptera: Braconidae), a key parasitoid of some caterpillar pests of vegetable crops in the USA. The greatest longevity (∼16days) was recorded for honey-fed wasps (positive control). Buckwheat significantly increased the lifespan of female and male wasps by at least two-fold relative to wasps provided water only (longevity=3–4days). Licorice mint significantly increased female longevity and numerically increased male longevity. Sweet alyssum slightly increased longevity of both sexes but this was not significantly different from the water only control. Females had a significantly longer longevity than males on all the diet treatments. The greatest carbohydrate nutrient levels (sugar content and glycogen) were recorded in honey-fed wasps followed by wasps fed buckwheat, whereas very little nutrients were detected in wasps provided sweet alyssum, licorice mint or water only. However, female wasps were observed to attempt to feed on all three flowering plant species. Thus, the low nutrient levels detected in wasps provided sweet alyssum or licorice mint may be because the nectars were not accessible or were of poor quality. Further studies will evaluate the effects of the promising farmscaping plants on the beneficial and pest insect communities in the field.

Observations on effect of seeding pattern on water-use efficiency of durum wheat in semi-arid areas of Morocco

Article

Dec 1998
FIELD CROP RES

Mohammed Karrou

In semi-arid areas of Morocco, soil evaporation is rapid during early growth period of durum wheat (Triticum turgidum cv. group durum). Experiments were conducted in the field during 1995–1996 and 1996–1997 to see if early shading of soil through the use of narrow row spacing and adequate plant population would help conserve water and hence increase wheat grain yield and water-use efficiency. Three seeding rates, 200, 300 and 400 kernelsm−2 and two distances between rows, 24cm (check) and 12cm were tested in a split-plot design. Results revealed that grain yield, total above-ground dry matter production and water-use efficiency were increased when row spacing was reduced. The effect of seeding rate was significant only in 1995–1996 where the highest plant population gave the lowest yield. Actual evapotranspiration measured for the whole growing season was not affected by any treatment. It appears that in semi-arid areas of Morocco, grain yield and water-use efficiency are more related to water use pattern during the growing season than to total evapotranspiration.

Multiple Comparisons and Multiple Tests Using SAS

Article

Jan 1999

Flower constancy in the hoverflies Episyrphus balteatus (Degeer) and Syrphus ribesii (L.) (Syrphidae)

Article

May 1998

The causes and consequences of flower constancy have been the focus of many studies, but almost all have examined the foraging behavior of bumblebees, honeybees, or butterflies. We test whether constancy occurs in an overlooked group of pollinators, the syrphid flies. Foraging sequences of wild flies of two species, Episyrphus balteatus and Syrphus ribesii, were examined when visiting flowers in seminatural plant communities and in artificial arrays of two color morphs of Lobularia maritima planted at a range of frequencies. Both species exhibited marked floral constancy when foraging in the mixed-plant community. Because all groups of pollinating insect so far examined exhibit constancy at least under some circumstances, we suggest that this is the predominant strategy used by pollinators and that there is probably a common explanation. Neither syrphid species exhibited constancy to different color morphs within a plant species, in contrast to previously published studies of Hymenoptera foraging among polymorphic flowers, which all describe positive frequency-dependent selection. Possible ex- planations for this discrepancy are discussed. We argue that constancy in these syrphids is unlikely to result from learning constraints on handling ability, currently the most widely accepted explanation for flower constancy, because they forage pri- marily for pollen which is easily located in most flowers they visit. Key words: color morph, foraging, handling time, hoverflies, interference, pollination, search image, Syrphidae. (Behav Ecoi 9:213-219 (1998))

Effects of Sweet Alyssum Flowers on the Longevity of the Parasitoid Wasps Cotesia marginiventris (Hymenoptera: Braconidae) and Diadegma insulare (Hymenoptera: Ichneumonidae)

Article

Mar 2000
FLA ENTOMOL

The effects of sweet alyssum (Lobularia maritima) (Brassicaceae) flowers on the longevity of two augmentatively-released parasitoids, Cotesia marginiventris (Cresson) (Hymenoptera: Braconidae) and Diadegma insulare (Cresson) (Hymenoptera: Ichneumonidae), were studied in a greenhouse experiment. C. marginiventris and D. insulare survived approximately 4.8 and 12.7 times longer, respectively, when provisioned with honey or with sweet alyssum than with water alone. Sweet alyssum planted in northern Florida cabbage fields may be one way to improve biological control by augmentatively-released natural enemies of lepidopteran pests by increasing adult parasitoid longevity during times when few wild plants are in bloom.

Using selective food plants to maximize biological control of vineyard pests

Article

May 2006
J APPL ECOL

Summary 1. Habitat manipulation is important for enhancing biological control of arthropod pests, but identification of selective food plants that benefit only natural enemies is required in order to avoid inadvertently exacerbating pest damage. 2. Greenhouse experiments were conducted to identify potential ground-cover plant species that would improve performance of the egg parasitoid Trichogramma carverae when mass released in vineyards to control the leafroller pest Epiphyas postvittana. Further experiments determined which plants increased immature survival and adult longevity of E. postvittana and a field experiment investigated field enhancement of biological control. 3. Greenhouse survival of T. carverae was greater in the presence of flowering shoots of Lobularia maritima than with flowering shoots of either Brassica juncea or Coriandrum sativum, or with shoots of any species from which flowers had been removed or a control with no shoots. Similar experiments with Fagopyrum esculentum and Borage officinalis showed survival was higher in the presence of shoots with flowers than in without-flower and control treatments. 4. Daily fecundity of T. carverae was greater in the presence of flowering shoots of L. maritima than F. esculentum and with treatments without flowers. There was no significant enhance- ment of fecundity with Brassica juncea and Borage officinalis flowers. 5. Adult longevity of male and female E. postvittana was as long in the presence of Borage officinalis and F. esculentum flowers as when fed a honey-based artificial diet but longevity was significantly lower than in the artificial diet treatment when caged with C. sativum and L. maritima, irrespective of whether flowers were present or not. 6. Larval development of E. postvittana on intact potted plants was lower on C. sativum and L. maritima than on Brassica juncea, Borage officinalis, F. esculentum and Trifolium repens (a known host of E. postvittana). 7. In the first and second 48-h periods after release of T. carverae in a field experiment, parasitism was significantly higher in pooled treatments with flowers (C. sativum, F. esculentum and L. maritima) than in pooled treatments without flowers (conventional ground-cover or bare earth). 8. Lobularia maritima provided clear benefit to T. carverae but was not used by adult and larval E. postvittana. 9. Synthesis and applications. Lobularia maritima is recommended as the selective food plant best suited to this system and its use beneath vines offers the additional advantage of suppressing weeds, so avoiding the need for herbicide applications and mechanical control.

Relative competitive performance of 63 species of terrestrial herbaceous plants

Article

Feb 2002
J VEG SCI

There is growing evidence that plant and animal species are arranged in hierarchies of relative competitive performance. More work is needed to determine which plant traits best predict relative competitive performance. We therefore measured relative competitive performance of 63 terrestrial herbaceous plant species using Trichostema brachiatum as a reference species (that is, phytometer or target species). The neighbour species came from a wide array of terrestrial vegetation types (e.g. rock barrens, alvars, old fields), and represented a wide array of growth forms (e.g. small rosette species such as Saxifraga virginiensis and large clonal graminoids such as Agropyron repens). The experiment was repeated with two pot sizes: large (control) and small (stress treatment). Relative competitive performance in large pots (controls) was highly correlated with that in small pots (stress treatment) (r= 0.90, p < 0.001). The hierarchy of relative competitive performance in the large pots was also highly correlated with the hierarchy in the small (stressed) pots (rs= 0.91, p < 0.001). Principal components analysis and multiple linear regression showed that plant size (measured by total biomass, above-ground biomass, below-ground biomass, canopy area, height and leaf area index) and leaf shape (measured as length to width ratio, length, width) were the two characteristics that best predicted relative competitive performance (large pots, r2= 0.55; small pots, r2= 0.48).

Seed ecology of a Mediterranean perennial herb with an exceptionally extended flowering and fruiting season

Article

Jul 2003
BOT J LINN SOC

Lobularia maritima is a Mediterranean short-lived herb with a flowering and fruiting season that lasts for ten months. Previous studies have shown that recruitment in periods other than autumn of the flowering season has few demographic implications; that is contributes little to the population growth rate. Since environmental conditions in periods other than autumn would allow recruitment, we examined to what extent the seed ecology of L. maritima accounts for recruitment shortage for the greater part of the year. To this end, we studied the effects of selfing and outcrossing on seed production and germination, within- and between-year variation in seed mass and germination, seed characteristics in the soil seed bank throughout the year, and the effect of temperature as a factor controlling seed germination. Results indicate that selfing does not decrease recruitment, and thus the observed changes in visitation rate and pollinator composition throughout the year cannot account for differences in recruitment. Germinability decreases throughout the year, suggesting a possible cost in reproduction associated with extended flowering. L. maritima has a transient seed bank whose seeds also experience a decrease in their germination throughout the year. Finally, temperature affects seed germination patterns, indicating the existence of quiescence mechanisms that prevent germination in the months prior to the summer drought. Overall, the results obtained support and, at least partly, explain the recruitment patterns of L. maritima observed in the field. © 2003 The Linnean Society of London, Botanical Journal of the Linnean Society, 2003, 142, 273–280.

Maximizing ecosystem services from conservation biological control: The role of habitat management

Article

May 2008

The intentional provision of flowering plants and plant communities in managed landscapes to enhance natural enemies is termed habitat management and is a relatively new but growing aspect of conservation biological control. The focus of most habitat management research has been on understanding the role of these plant-provided resources on natural enemy biology, ecology, and their ability to enhance suppression of pest populations. Far less attention has been paid to additional ecosystem services that habitat management practices could provide in managed landscapes. We first evaluate whether habitat management is well positioned to advance in these areas. Our analysis of past habitat management studies indicates that four plant species have been tested in the majority of field evaluations, while plants native to the test area and perennial plants are particularly underrepresented. We suggest that synergies among biodiversity conservation, ecological restoration, human cultural values, tourism, biological control and other ecosystem services have largely been overlooked in past habitat management research and we illustrate how these potential ecosystem services could be evaluated and enhanced. We then review two case studies in which broader ecosystem services were explicitly addressed in plant selection criteria. One case study demonstrates that native plants useful in restoration of rare ecosystems can increase natural enemy abundance as much as widely recommended non-natives. The second addresses additional ecosystem services provided by habitat management in New Zealand vineyards. We conclude that addressing ‘stacked’ ecosystem services with multiple ecosystem service goals can decrease agriculture’s dependence on ‘substitution’ methods such as the current reliance on oil-based agro-chemical inputs.

Recent advances in conservation biological control of arthropods by arthropods

Article

May 2008
BIOL CONTROL

Conservation biological control (CBC) aims at improving the efficacy of natural enemies and can contribute to safer and more effective biological control practices. Considerable progress in this field has been made during recent years, and it is therefore justified to review key findings in a special issue of Biological Control. The following topics, with primary emphasis on CBC of arthropods by arthropods are covered in this issue: (1) honeydew as a food source for natural enemies, (2) artificial food sprays, (3) shelter habitats, (4) chemical ecology and CBC, (5) natural enemy diversity and CBC, (6) CBC at a landscape scale, (7) CBC as provider of multiple ecosystem services, and (8) economics and adoption of CBC. These reviews present substantial evidence that CBC can attract and/or improve the fitness of natural enemies. However, studies showing that this translates into decreased pest damage, increased crop yield or quality and improved economic profit for growers are still rare. We conclude that future researchers should investigate the effect of CBC at these levels, but also that we need a better understanding of which conditions CBC will reduce pest populations in the field. CBC has the potential to increase ecosystem services other than biological control and consideration of the economic benefits of this will increase the likelihood of adoption of CBC.

Flower color affects tri-trophic biocontrol interactions

Article

Jul 2004

The adults of many parasitoid species require nectar for optimal fitness, but very little is known of flower recognition. Flight cage experiments showed that the adults of an egg parasitoid (Trichogramma carverae Oatman and Pinto) benefited from alyssum (Lobularia maritima L.) bearing white flowers to a greater extent than was the case for light pink, dark pink or purple flowered cultivars, despite all cultivars producing nectar. Survival and realised parasitism on all non-white flowers were no greater than when the parasitoids were caged on alyssum shoots from which flowers had been removed. The possibility that differences between alyssum cultivars were due to factors other than flower color, such as nectar quality, was excluded by dying white alyssum flowers by placing the roots of the plants in 5% food dye (blue or pink) solution. Survival of T. carverae was lower on dyed alyssum flowers than on undyed white flowers. Mixing the same dyes with honey in a third experiment conducted in the dark showed that the low level of feeding on dyed flowers was unlikely to be the result of olfactory or gustatory cues. Flower color appears, therefore, to be a critical factor in the choice of plants used to enhance biocontrol, and is likely also to be a factor in the role parasitoids play in structuring invertebrate communities.

Effects of alyssum flowers on the longevity, fecundity, and sex ratio of the leafroller parasitoid Dolichogenidea tasmanica

Article

Jan 2005

A laboratory experiment assessed the effect of floral food resources on the longevity, fecundity, and sex ratio of Dolichogenidea tasmanica (Cameron) (Hymenoptera: Braconidae), a parasitoid of leafrollers (Lepidoptera: Tortricidae). Alyssum (Lobularia maritima (L.), Brassicaceae) plants with flowers were compared with plants without flowers, with water available in both treatments. Adult parasitoids were provided with an excess of second-instar larval hosts, which were then reared to determine the composition of the F1 parasitoid generation. Female parasitoids with access to alyssum flowers lived, on average, seven times longer than those without flowers. Male longevity was three times greater with, than without flowers. The lifetime realised fecundity of D. tasmanica was also significantly increased in the presence of flowers, although this was a consequence of the increase in longevity, rather than an increase in daily fecundity. Without flowers, offspring sex ratios were strongly male biased, but when females had access to flowers an approximately equal sex ratio was produced. These results are discussed in relation to the use of flowers in agroecosystems for the conservation biological control of leafroller pests.

The influence of flower morphology and nectar quality on the longevity of a parasitoid biological control agent

Article

Nov 2006

Conservation biological control aims to enhance the efficacy of arthropod biological control agents, such as parasitoids, partly by providing them with access to floral nectar. However, the suitability of a flower species for providing nectar to a parasitoid is dependent on the morphologies of the parasitoid and the flower, as well as on the quality of the nectar. The effects of seven flower species on the longevity of Microctonus hyperodae (Hymenoptera Braconidae), a parasitoid of the Argentine stem weevil, Listronotus bonariensis (Coleoptera: Curculionidae), were measured in the laboratory. The flowers were phacelia (Phacelia tanacetifolia), buckwheat (Fagopyrum esculentum), alyssum (Lobularia maritima), coriander (Coriandrum sativum), white clover (Trifolium repens), red clover (Trifolium pratense) and white mustard (Sinapis alba). The results suggested M. hyperodae was unable to reach nectar of red clover, white clover, alyssum and phacelia, but was able to gain access to the nectar of the other three species. However, only buckwheat and coriander increased its longevity. Flower corolla aperture and depth probably determined the parasitoid’s access to nectar. Accessible nectars were analyzed for sugar composition and the effect of the sucrose/(glucose + fructose) ratio on nectar suitability was assessed. The relevance of these results to other hymenopteran parasitoid species is discussed in terms of selecting the most appropriate floral diversity in agricultural extensification programmes.

A comparative approach to predicting competitive ability from plant traits

Article

Jul 1988

Decades of study of interspecific competition in community ecology has yielded an overwhelming body of special cases but few general principles1-3. This is largely because of the phenomenological, non-predictive approach used4. Further progress requires a predictive approach5 that will enable general principles to be deduced that apply beyond the species and conditions of a particular study or site. General principles are best sought using a comparative approach, that is, the systematic screening of a large number of species under standardized experimental conditions6,7 We used 44 wetland plant species to test whether competitive ability could be predicted from plant traits. Multiple linear regression showed that there was a strong relationship between plant traits and competitive ability (r2 Combining double low line 0.74). Plant biomass explained 63% of the variation in competitive ability and plant height, canopy diameter, canopy area and leaf shape explained most of the residual variation. This study represents a major step in escaping the current phenomenological approach to competition in community ecology, and provides a general predictive tool for studying competition in natural communities.

Food sources for adult Diachasmimorpha longicaudata, a parasitoid of tephritid fruit flies: effects on longevity and fecundity

Article

Mar 2006

We report the results of a study on potential food sources of the widely distributed Indo-Australian braconid fruit fly parasitoid Diachasmimorpha longicaudata (Ashmead) (Hymenoptera: Braconidae). Adults sustained life on diets of fruit juice or fruit pulp, a homopteran and its associated honeydew, or extrafloral nectary secretions. Longevities on all these foods and fecundity on fruit juice were comparable to those achieved on the honey that is typically provided in mass-rearing programs. Certain of the flower species Bidens alba (L.), Spermacoce verticillata L., Lobularia maritima (L.) Desv., Brassica nigra (L.), Lantana camara L., their nectar or pollen, provided a diet that resulted in longer maximum life spans than water alone. Unlike some tephritid flies, the braconid did not feed on fresh bird feces or leaf-surface exudates. Feeding by D. longicaudata on wounded host fruits of tephritid flies suggests that adult parasitoids would not need separate forays for adult food and oviposition sites, as these occur in the same locations. We conclude that an inventory of adult foods may help target inundative releases of D. longicaudata and lead to improvements in diets used for mass rearing.

IPM for fresh-market lettuce production in the desert southwest: The produce paradox

Article

Dec 2009
PEST MANAG SCI

In the 'Integrated Control Concept', Stern et al. emphasized that, although insecticides are necessary for agricultural production, they should only be used as a last resort and as a complement to biological control. They argued that selective insecticide use should only be attempted after it has been determined that insect control with naturally occurring biotic agents is not capable of preventing economic damage. However, they concluded their seminal paper by emphasizing that integrated control will not work where natural enemies are inadequate or where economic thresholds are too low to rely on biological control. Thus, it is no surprise that insect control in high-value, fresh-market lettuce crops grown in the desert southwest have relied almost exclusively on insecticides to control a complex of mobile, polyphagous pests. Because lettuce and leafy greens are short-season annual crops with little or no tolerance for insect damage or contamination, biological control is generally considered unacceptable. High expectations from consumers for aesthetically appealing produce free of pesticide residues further forces vegetable growers to use chemical control tactics that are not only effective but safe. Consequently, scientists have been developing integrated pest management (IPM) programs for lettuce that are aimed at reducing the economic, occupational and dietary risks associated with chemical controls of the past. Most of these programs have drawn upon the integrated control concept and promote the importance of understanding the agroecosystem, and the need to sample for pest status and use action thresholds for cost-effective insect control. More recently, pest management programs have implemented newly developed, reduced-risk chemistries that are selectively efficacious against key pests. This paper discusses the influence that the integrated control concept, relative to zero-tolerance market standards and other constraints, has had on the adoption of pest management in desert lettuce crops.

Synergy between chemical and biological control in the IPM of currant-lettuce aphid (Nasonovia ribisnigri) in Canterbury, New Zealand

Article

Aug 2009

Field trials were conducted at four Canterbury, New Zealand locations in 2005-06 to determine if the synergistic effects of biological control by natural enemies and standard drenching techniques controlled lettuce aphid populations throughout the entire growing season. Chemical usage significantly lowered aphid densities in the outer, wrapper and heart leaves compared to control plants at most times. However, in mid-summer, natural enemies, such as the brown lacewing (Micromus tasmaniae), 11-spotted ladybird beetle (Coccinella undecimpunctata) and small hoverfly larvae (Melanostoma fasciatum), were more than sufficient to control lettuce aphids without the use of insecticides. Drenching, in addition to natural enemy attack, appears to be required in early spring and late summer to maintain very low levels of lettuce aphid. Given the potential for imidacloprid resistance to develop, it may be advisable to restrict drenches to these key periods in order to allow populations of natural enemies to maintain control of prey populations. We recommend industry support the validation of action thresholds across different regions within New Zealand and focus on the seasonal biology of predators to assist growers with the sustainable long-term control of lettuce aphids. The inclusion of additional data into an economic model to compare pest damage with predator loading would be useful for growers in managing aphid problems. These results will assist in the continued improvement and development of a sustainable IPM strategy for lettuce aphids in New Zealand and elsewhere.

Inference by eye: Reading the overlap of independent confidence intervals

Article

Jan 2009

Geoff Cumming

When 95 per cent confidence intervals (CIs) on independent means do not overlap, the two-tailed p-value is less than 0.05 and there is a statistically significant difference between the means. However, p for non-overlapping 95 per cent CIs is actually considerably smaller than 0.05: If the two CIs just touch, p is about 0.01, and the intervals can overlap by as much as about half the length of one CI arm before p becomes as large as 0.05. Keeping in mind this rule-that overlap of half the length of one arm corresponds approximately to statistical significance at p = 0.05-can be helpful for a quick appreciation of figures that display CIs, especially if precise p-values are not reported. The author investigated the robustness of this and similar rules, and found them sufficiently accurate when sample sizes are at least 10, and the two intervals do not differ in width by more than a factor of 2. The author reviewed previous discussions of CI overlap and extended the investigation to p-values other than 0.05 and 0.01. He also studied 95 per cent CIs on two proportions, and on two Pearson correlations, and found similar rules apply to overlap of these asymmetric CIs, for a very broad range of cases. Wider use of figures with 95 per cent CIs is desirable, and these rules may assist easy and appropriate understanding of such figures.

Role of Syrphid Larvae and Other Predators in Suppressing Aphid Infestations in Organic Lettuce on California’s Central Coast

Article

Nov 2008
J ECON ENTOMOL

Organic lettuce, Lactuca sativa L., growers on the Central Coast of California rely on conservation biological control to manage Nasonovia ribisnigri Mosley (Hemiptera: Aphididae) and other aphid pests of lettuce. In 2006, we carried out five replicated field trials to determine the importance of syrphid larvae in the suppression of N. ribisnigri and other aphids infesting organic romaine lettuce. We used Entrust, a spinosad-based insecticide approved for use on organic farms, to suppress syrphid larvae in aphid-infested romaine. Romaine treated with Entrust was unmarketable at harvest because of aphid infestation, whereas insecticide-free romaine was marketable. Syrphid larvae composed 85% or more of total predators in most trials, and they were the only predators consistently recovered from romaine that was infested with aphids early and largely aphid-free by harvest. The species mix of nonsyrphid predators varied from site to site. Applications of Entrust suppressed nonsyrphid predators in two trials, and so was an imperfect tool for selectively suppressing syrphid larvae. The relative importance of syrphid larvae and other predators in the conservation biological control of aphids in organic romaine is discussed. We conclude that syrphid larvae are primarily responsible for the suppression of aphids in organic romaine on California's Central Coast.

A century of plant virus management in the Salinas Valley of California, ‘East of Eden’

Article

Dec 2000
VIRUS RES

The mild climate of the Salinas Valley, CA lends itself well to a diverse agricultural industry. However, the diversity of weeds, crops and insect and fungal vectors also provide favorable conditions for plant virus disease development. This paper considers the incidence and management of several plant viruses that have caused serious epidemics and been significant in the agricultural development of the Salinas Valley during the 20th century. Beet curly top virus (BCTV) almost destroyed the newly established sugarbeet industry soon after its establishment in the 1870s. A combination of resistant varieties, cultural management of beet crops to provide early plant emergence and development, and a highly coordinated beet leafhopper vector scouting and spray programme have achieved adequate control of BCTV. These programmes were first developed by the USDA and still operate. Lettuce mosaic virus was first recognized as causing a serious disease of lettuce crops in the 1930s. The virus is still a threat but it is controlled by a lettuce-free period in December and a seed certification programme that allows only seed lots with less than one infected seed in 30000 to be grown. 'Virus Yellows' is a term used to describe a complex of yellows inducing viruses which affect mainly sugarbeet and lettuce. These viruses include Beet yellows virus and Beet western yellows virus. During the 1950s, the complex caused significant yield losses to susceptible crops in the Salinas Valley. A beet-free period was introduced and is still used for control. The fungus-borne rhizomania disease of sugarbeet caused by Beet necrotic yellow vein virus was first detected in Salinas Valley in 1983. Assumed to have been introduced from Europe, this virus has now become widespread in California wherever beets are grown and crop losses can be as high as 100%. Movement of infested soil and beets accounts for its spread throughout the beet-growing regions of the United States. Control of rhizomania involves several cultural practices, but the use of resistant varieties is the most effective and is necessary where soils are infested. Rhizomania-resistant varieties are now available that perform almost as well as the non-resistant varieties under non-rhizomania conditions. Another soil-borne disease termed lettuce dieback, caused by a tomato bushy stunt-like tombusvirus, has become economically limiting to romaine and leaf lettuce varieties. The virus has no known vector and it seems to be moved through infested soil and water. Heavy rains in the past 4 years have caused flooding of the Salinas River and lettuce fields along the river have been affected severely by dieback. Studies are now in progress to characterize this new virus and identify sources of resistance. Agriculture in the Salinas Valley continues to grow and diversify, driven by demands for 'clean', high quality food by the American public and for export. The major aspects of plant virus control, including crop-free periods, breeding for resistance, elimination of inoculum sources, and vector control will continue to be vital to this expansion. Undoubtedly, the advances in crop production through genetic manipulation and advances in pest management through biological control will eventually become an important part of agricultural improvement.

A Survey of Syrphid Predators of Nasonovia ribisnigri in Organic Lettuce on the Central Coast of California

Article

Mar 2007
J ECON ENTOMOL

Organic lettuce, Lactuca sativa L

Agronomic aspects of strip intercropping lettuce with alyssum for biological control of aphids

Abstract

No full-text available