Exploring entomopathogenic nematodes for the management of Lobesia botrana (Lepidoptera: Tortricidae) in vineyards: Fine-tuning of application, target area, and timing
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... Although research on using EPNs as biocontrol agents in vineyard agroecosystems remains an area yet to be exhaustively explored, numerous studies have begun to delve into their applications against a range of aerial pests plaguing vineyards (Campos-Herrera et al., 2021). Potential targets include Planococcus ficus (Hemiptera: Pseudococcidae), Philaenus spumarius (Hemiptera: Aphrophoridae), Thaumatotibia leucotreta, Lobesia botrana (Lepidoptera: Tortricidae), and Vitacea polistimorfis (Lepidoptera: Sessidae) (Williams et al., 2010;Vieux and Malan, 2015;Steyn et al., 2021;Vicente-Díez et al., 2021a, 2021bCampos-Herrera et al., 2023). However, for this promising approach to materialize, it is imperative to consider the compatibility of specific EPN populations with the common agrochemical applications concurrently employed in vineyard management. ...
... All products were promptly prepared upon their arrival at the laboratory to ensure optimal experimental conditions. Following procedures described by Campos-Herrera et al. (2023), each agrochemical was prepared by doubling the highest recommended field dose for a final volume of 0.5 L. Subsequently, each preparation was combined with the nematode-adjusted concentration in a 1:1 ratio, yielding a final fungicide concentration equal to the maximum field application dosage. All the experiments were repeated with a new mixture of the product and nematode preparations. ...
... Viability test: The experimental procedure followed the methodologies described by Campos-Herrera et al. (2023). A nematode concentration of 20 IJs/100 mL per EPN population was prepared to investigate nematode survival following agrochemical exposure. ...
Vineyards, covering over seven million hectares worldwide, hold significant socio-cultural importance. Traditionally reliant on conventional practices and agrochemicals, this agroecosystem faces environmental challenges, including soil and water pollution. Sustainable viticulture, driven by eco-friendly practices and cost reduction, has gained prominence, underlining the importance of biological control agents such as entomopathogenic nematodes (EPNs). EPNs naturally occurr in vineyard soils and play a crucial role in controlling pest damage. Ensuring compatibility between EPNs and the commonly used vineyard fungicides is critical, as these applications constitute the predominant pest-management practice during the productive grapevine cycle.
This study assessed the impact of authorized grapevine fungicides on EPNs, focusing on the survival of populations and sublethal effects on their virulence. We investigated the compatibility of two EPN populations ( Steinernema feltiae 107 and S. carpocapsae ‘All’) with three organic production-approved products ( Bacillus pumilus , sulfur, and copper oxychloride) and two synthetic chemicals (Trifloxystrobin and Mancozeb). Our findings revealed that the viability of S. feltiae 107 was reduced when exposed to sulfur and copper oxychloride, and its virulence was affected by copper oxychloride and Mancozeb, although only two days after exposure and with no significant differences for larval mortality at five days.
In contrast, S. carpocapsae ‘All’ exhibited full compatibility with all five fungicides, with no impact on its viability or virulence. Consequently, our results suggested that the evaluated fungicides could be co-applied on both EPN populations if they were employed on the same day. However, further research on multi-target interactions is needed to ensure the successful implementation of this kind of co-application.
... Additionally, various biological control strategies are being explored to combat this pest, including the use of predators such as insects, other arthropods, vertebrates (Coscollá, 1996;Ioriatti et al., 2011;Thiéry & Desneux, 2018), microorganisms such as entomopathogenic fungi and Bacillus thuringiensis (Beris et al., 2024;Vicente-Díez et al., 2021), and entomopathogenic nematodes (Campos-Herrera et al., 2023). ...
The grapevine moth Lobesia botrana is a major pest of vineyards worldwide. Chemical insecticides and the sexual confusion technique are used to reduce damage. Several biological control approaches are being studied, including the use of the obligate intracellular bacteria Wolbachia, however, this method has been little explored. To use this bacterium for pest control it is necessary to know if the target pest is infected. The aim of this study was to examine Wolbachia infection in L. botrana populations from different vine growing areas of San Juan, Argentina. Lobesia botrana were captured in vineyards using sticky traps with pheromones. Wolbachia infection was diagnosed using a specific PCR test and fully characterized using Multi-Locus Sequence Typing (MLST) analyses. All populations tested were positive for Wolbachia, representing the first record of Wolbachia strains in grapevine moths from Argentina. The MLST analyses showed that Wolbachia strain belongs to supergroup B, clustering with other Wolbachia moth strains. More research is needed to understand the relationship between the grapevine moth and Wolbachia and how to use this to manage pests.
... For in vitro studies, Campos-Herrera et al. (2023a) showed that exposure of IJs of steirnernematids and heterorhabditids to commercial adjuvants did not affect the viability of EPNs but did reduce the infectivity after two days of S. feltiae 107, S. feltiae Koppert and H. bacteriophora VM-21 exposed during 24 h to these chemicals. Additionally, exposure to copper and sulfur fungicides negatively affected the viability and virulence of S. feltiae without affecting S. carpocapsae (Campos-Herrera et al., 2023b). Our results showed that the presence of CFS in the plant-mesocosm system, as a potential nematicidal product, negatively affected EPN, particularly steinernematids. ...
... To protect grapevines, growers implement integrated pest management (IPM) plans, which incorporate cultural, biological, mechanical, and physical controls to mitigate yield losses and decrease insect pressure [5][6][7]. Some examples of strategies include exclusion [8], trapping [9], planting resistant varieties [10], and biocontrol [11,12]. However, if these methods are insufficient, chemical controls (insecticides) are often implemented, and are typically effective [13], but can have detrimental environmental effects [14,15]. ...
Background
Grapevine (Vitis) is one of the world’s most valuable fruit crops, but insect herbivory can decrease yields. Understanding insect herbivory resistance is critical to mitigating these losses. Vitis labrusca, a wild North American grapevine species, has been leveraged in breeding programs to generate hybrid grapevines with enhanced abiotic and biotic stress resistance, rendering it a valuable genetic resource for sustainable viticulture. This study assessed the resistance of V. labrusca acc. ‘GREM4’ and Vitis vinifera cv. ‘PN40024’ grapevines to Popillia japonica (Japanese beetle) herbivory and identified morphological and genetic adaptations underlying this putative resistance.
Results
‘GREM4’ displayed greater resistance to beetle herbivory compared to ‘PN40024’ in both choice and no-choice herbivory assays spanning periods of 30 min to 19 h. ‘GREM4’ had significantly higher average leaf trichome densities than ‘PN40024’ and beetles preferred to feed on the side of leaves with fewer trichomes. When leaves from each species that specifically did not differ in trichome densities were fed on by beetles, significantly less leaf area was damaged in ‘GREM4’ (3.29mm²) compared to ‘PN40024’ (9.80mm²), suggesting additional factors beyond trichomes contributed to insect herbivory resistance in ‘GREM4’. Comparative transcriptomic analyses revealed ‘GREM4’ exhibited greater constitutive (0 h) expression of defense response and secondary metabolite biosynthesis genes compared to ‘PN40024’, indicative of heightened constitutive defenses. Upon herbivory, ‘GREM4’ displayed a greater number of differentially expressed genes (690) compared to ‘PN40024’ (502), suggesting a broader response. Genes up-regulated in ‘GREM4’ were enriched in terpene biosynthesis, flavonoid biosynthesis, phytohormone signaling, and disease defense-related functions, likely contributing to heighted insect herbivory defense, while genes differentially expressed in ‘PN40024’ under herbivory were enriched in xyloglucan, cell wall formation, and calcium ion binding. The majority of genes implicated in insect herbivory defense were orthologs with specific expression patterns in ‘GREM4’ and ‘PN40024’, but some paralogous and genome-specific genes also likely contributed to conferring resistance.
Conclusions
Our findings suggest that ‘GREM4’ insect herbivory resistance was attributed to a combination of factors, including trichomes and unique constitutive and inducible expression of genes implicated in terpene, flavonoid, and phenylpropanoid biosynthesis, as well as pathogen defense.
... This study highlights how the nematode entomopathogenic activity reduces the EGVM population at various stages (L3 and pupa) and related damage on grape bunches, being able to confer certain control to the possible overwintering stage. Overall, Campos-Herrera et al. (2023) suggested that the optimal EPN application would be at sunset during late spring/early autumn at mid-temperatures (15-22 • C). Finally, a recent study performed with the entomopathogenic symbiotic bacteria of the EPN has probed that exposure of the bacterial ferment against EGVM had anti-ovipositional activity for three days as well as larval feeding deterrent effects on grapes, reducing the overall damage (Vicente-Díez et al., 2023c). ...
The grapevine moth, Lobesia botrana (Lepidoptera: Tortricidae), is a critical pest for vineyards and causes significant economic losses in wine-growing areas worldwide. Identifying and developing novel semiochemical cues (e.g. volatile bacterial compounds) which modify the ovipositional and trophic behaviour of L. botrana in vineyard fields could be a novel control alternative in organic viticulture. Xenorhabdus spp. and Photorhabdus spp. are becoming one of the best-studied bacterial species due to their potential interest in producing toxins and deterrent factors. In this study, we investigated the effect of the deterrent compounds produced by Xenorhabdus nematophila and Photorhabdus laumondii on the ovipositional moth behaviour and the larval feeding preference of L. botrana. Along with the in-vitro bioassays performed, we screened the potential use of 3 d cell-free bacterial supernatants and 3 and 5 d unfiltered bacterial ferments. In addition, we tested two application systems: (i) contact application of the bacterial compounds and (ii) volatile bacterial compounds application. Our findings indicate that the deterrent effectiveness varied with bacterial species, using bacterial cell-free supernatants or unfiltered fermentation product, and the culture times. Grapes soaked in the 3 d X. nematophila and P. laumondii ferments had ∼55% and ∼95% fewer eggs laid than the control, respectively. Likewise, the volatile compounds emitted by the 5 d P. laumondii fermentations resulted in ∼100% avoidance of L. botrana ovipositional activity for three days. Furthermore, both bacterial fermentation products have larval feeding deterrent effects (∼65% of the larva chose the control grapes), and they significantly reduced the severity of damage caused by third instar larva in treated grapes. This study provides insightful information about a novel bacteria-based tool which can be used as an eco-friendly and economical alternative in the integrated control of L. botrana vineyard pests.
The entomopathogenic nematodes (EPNs) are biological control agents that are widespread in crop soils. However, traditional agricultural management practices such as cultivation and agrochemical usage can alter the soil balance that enables their occurrence and activity. Alternative strategies like mulching, are commonly employed to prevent weed growth, enhance below-ground biodiversity by improving soil, organic matter content, fertility, and moisture. We hypothesized that organic mulches would favor biotic conditions for nematofauna development in crop soil, including EPNs, compared to herbicide application or tillage. Traditional (insect baits) and molecular (qPCR analysis) tools were used in this study to assess the abundance and activity of native EPNs, and the abundance of potential natural enemies, such as free-living nematode (FLN) competitors, nematophagous fungi (NF), and ectoparasitic bacteria, in soils managed with different organic mulches or traditional practices. As a model agroecosystem, we selected the vineyard, one of the most intensively managed crop systems. We compared mulches of grape pruning debris (GPD-M), straw (Str-M), and spent mushroom compost (SMC-M) in two commercial vineyards, which employed either integrated or organic pest and disease management. Following a completely randomized design, we retrieved two composite samples per plot (n=3 per vineyard) in April, June, and October 2020. Numbers of EPNs and selected members of their soil food web were higher in the organic than the integrated managed vineyard. Supporting our hypothesis, organic mulching overall favored nematode occurrence in both vineyards. We found higher NF abundance for Str-M, and GPD-M in the organic vineyard, which plausibly explained the lower EPN activity and occurrence compared to SMC-M in both vineyards. We conclude that the organic mulches can provide appropriate conditions for increasing nematofauna numbers but, depending on the mulch type, may also adversely affect EPNs by increasing their natural enemies. Our findings highlight the need to explore alternative farming practices to unravel complex biotic interactions that affect beneficial soil organisms in agroecosystems.
Entomopathogenic nematodes (EPN) species differ in their capability to withstand rapid desiccation (RD). Infective juveniles of Steinernema carpocapsae are a better adaptable and tolerant than Steinernema feltiae or Heterorhabditis bacteriophora as, an optimal RH of > 90% is required by S. feltiae and H. bacteriophora while maintaining RH equivalent to 74% could sustain survival of S. carpocapsae under RD. Our findings from infectivity suggest that following application, shrunk IJs are acquired passively by the larvae, probably rehydrate and resume infection within the insect gut. Water loss rate is a key factor affecting survival of S. carpocapsae on exposed surfaces. The present study provides the foundation for characterizing mechanism of rapid rate of water loss in EPN. ATR-FTIR is a rapid and reliable method for analysis of water loss. Changes in peak intensity was observed at 3100–3600 cm⁻¹ (OH bonds of water), 2854 cm⁻¹ (CH stretching of symmetric CH2, acyl chains), 2924 cm⁻¹ (CH stretching of anti-symmetric CH2, lipid packing heterogeneity), 1634 cm⁻¹ (amide I bonds) indicate major regions for hydration dependent changes in all EPN species. FTIR data also indicates that, S. carpocapsae contains strong water interacting regions in their biochemical profile, which could be an influencing factor in their water holding capacity under RD. ATR-FTIR were correlated to water content determined gravimetrically by using Partial Least square –Regression and FTIR multivariate method, which could be used to screen a formulation’s potential to maintain or delay the rate of water loss in a rapid and efficient manner.
Vineyards and their associated socio-economic activities are relevant sectors worldwide. Still, this agroecosystem is one of the most intensely managed crops and erosion-prone land areas. The conventional viticulture practices to control pests, diseases, and weeds, like tillage and agrochemical applications, accelerate the loss of soil biodiversity and compromise the presence of beneficial soil organisms such as the entomopathogenic nematodes (EPNs). Such human disturbances in the agroecosystems can strongly affect abiotic (e.g., soil texture and properties) and biotic factors (natural enemies and potential competitors) that modulate the EPN activity as biological control agents. For the first time in viticulture, this study aimed to investigate the impact of differentiating management on the EPN community and associated soil organisms and if their assemblage will provide indicators of better practices for sustainable farming. We hypothesized that organic pest management and alternative strategies to tillage might enhance the abundance and activity of the native EPN community in vineyard soils. In autumn 2019, we collected two composite soil samples from 80 vineyards distributed across the Guaranteed Designation of Origin (denominated DOCa) Rioja region. The sites belonged to one category of each of the two factors: pest management (integrated vs. organic, 40 plots each) and soil managing (tillage vs. cover cropping, 48 and 32 vineyards, respectively). Isolated through sucrose-gradient centrifugation and employing species-specific primers/probe qPCR sets, we investigated the presence of ten EPN species and associated soil organisms: four free-living nematodes (FLNs), six nematophagous fungi (NF), and two ectoparasitic bacteria (EcPB). Besides, we estimated the EPN activity using the traditional insect-bait method. We included in the analysis twenty soil variables to characterize the evaluated treatments and assess their impact on soil organism distribution. Our results provide evidence on the support of organic viticulture to beneficial soil organisms, notably the activity of native EPNs. We also reported a higher abundance of S. feltiae (the predominant steinernematid species in Europe) and FLNs for organic farming than IMP, while the presence of NF and EcPB resulted in unaffected. Contrarily, the soil management practices considered did not differ in their impact on EPNs or their natural enemies/competitors, even if contrasted for several soil properties. Future research may expand the screened soil-dwelling species using novel molecular technics to unravel their complex interactions and determine the best farming practices to preserve soil health.
The European grapevine moth (Lobesia botrana; Denis and Schiffermüller, 1775) is considered a key pest for grapevine (Vitis vinifera L.) in the Douro Region, Portugal. The phenology of both the grapevine and the pest has changed in the last decades due to the increase in temperature. Here, we assess the potential impact of climate change on the (a)synchrony of both species. The results show that the phenological stages (budburst, flowering and veraison) undergo an advancement throughout the region (at an ~1 km resolution) under a climate change scenario (Representative Concentration Pathways, RCP8.5) for the period 2051–2080, with respect to the historic period (1989–2015). For cv. Touriga Nacional and Touriga Franca, the budburst advances up to 14 days, whereas for flowering and veraison the advancements are up to 10 days (mainly at low elevations along the Douro River). For the phenology of Lobesia botrana, earliness was also verified in the three flights (consequently there may be more generations per year), covering the entire region. Furthermore, the third flight advances further compared to the others. For both varieties, the interaction between the third flight (beginning and peak) and the veraison date is the most relevant modification under the future climate change scenario (RCP8.5, 2051–2080). The aforementioned outcomes from the phenology models help to better understand the possible shifts of both trophic levels in the region under future climate, giving insights into their future interactions.
The European grapevine moth (EGVM) Lobesia botrana (Lepidoptera: Tortricidae) is a relevant pest in the Palearctic region vineyards and is present in the Americas. Their management using biological control agents and environmentally friendly biotechnical tools would reduce intensive pesticide use. The entomopathogenic nematodes (EPNs) in the families Steinernematidae and Heterorhabditidae are well-known virulent agents against arthropod pests thanks to symbiotic bacteria in the genera Xenorhabdus and Photorhabdus (respectively) that produce natural products with insecticidal potential. Novel technological advances allow field applications of EPNs and those bioactive compounds as powerful bio-tools against aerial insect pests. This study aimed to determine the viability of four EPN species (Steinernema feltiae, S. carpocapsae, S. riojaense, and Heterorhabditis bacteriophora) as biological control agents against EGVM larval instars (L1, L3, and L5) and pupae. Additionally, the bioactive compounds from their four symbiotic bacteria (Xenorhabdus bovienii, X. nematophila, X. kozodoii, and Photorhabdus laumondii subsp. laumondii, respectively) were tested as unfiltered ferment (UF) and cell-free supernatant (CFS) against the EGVM larval instars L1 and L3. All of the EPN species showed the capability of killing EGVM during the larval and pupal stages, particularly S. carpocapsae (mortalities of ~50% for L1 and >75% for L3 and L5 in only two days), followed by efficacy by S. feltiae. Similarly, the bacterial bioactive compounds produced higher larval mortality at three days against L1 (>90%) than L3 (~50%), making the application of UF more virulent than the application of CFS. Our findings indicate that both steinernematid species and their symbiotic bacterial bioactive compounds could be considered for a novel agro-technological approach to control L. botrana in vineyards. Further research into co-formulation with adjuvants is required to expand their viability when implemented for aboveground grapevine application.
Vineyards face several biotic threats that compromise the grape quality and quantity. Among those that cause relevant economic impact and have worldwide distribution are the oomycete Plasmopara vitícola, the fungi Erysiphe necator and Botrytis cinerea, and the arthropods Lobesia botrana, Tetranychus urticae, and Phylaenus spumarius (principal vector of the bacterial disease Xylella fastidiosa in Europe). Their management relies primarily on agrochemicals with short persistence; widespread use of these chemicals causes environmental and human health problems. The challenge of sustainable viticulture is to provide ecologically sound alternatives. In this regard, the application of entomopathogenic nematodes (EPNs) and natural products derived from their symbionts can be an alternative. EPNs are well-known biocontrol agents for soil-dwelling insects. However, current research demonstrates the great potential of both EPN and their derivates as direct bio-tools against some of the key fungal and arthropods pests present aboveground. In addition, recent evidence shows that detecting EPN presence and activity and their relation with other soil organisms associated with them can help us to understand the impact of different agricultural practices on vineyard management. Altogether, this review illustrates the great potential of EPN to enhance pest and disease management in the next generation of viticulture.
Our study aimed to identify the novel acaricidal compound in Xenorhabdus szentirmaii and X. nematophila using the easyPACId approach (easy Promoter Activated Compound Identification). We determined the (1) effects of cell-free supernatant (CFS) obtained from mutant strains against T. urticae females , (2) CFS of the acaricidal bioactive strain of X. nematophila (pCEP_kan_XNC1_1711) against different biological stages of T. urticae, and females of predatory mites, Phytoseiulus persimilis and Neoseiulus californicus , (3) effects of the extracted acaricidal compound on different biological stages of T. urticae, and (4) cytotoxicity of the active substance. The results showed that xenocoumacin produced by X. nematophila was the bioactive acaricidal compound, whereas the acaricidal compound in X. szentirmaii was not determined. The CFS of X. nematophila (pCEP_kan_XNC1_1711) caused 100, 100, 97.3, and 98.1% mortality on larvae, protonymph, deutonymph and adult female of T. urticae at 7 dpa in petri dish experiments; and significantly reduced T. urticae population in pot experiments. However, the same CFS caused less than 36% mortality on the predatory mites at 7dpa. The mortality rates of extracted acaricidal compound (xenocoumacin) on the larva, protonymph, deutonymph and adult female of T. urticae were 100, 100, 97, 96% at 7 dpa. Cytotoxicity assay showed that IC 50 value of xenocoumacin extract was 17.71 μg/ml after 48 h. The data of this study showed that xenocoumacin could potentially be used as bio-acaricide in the control of T. urticae; however, its efficacy in field experiments and its phytotoxicity need to be assessed in future.
Citation: Vicente-Díez, I.; Blanco-Pérez, R.; González-Trujillo, M.d.M.; Pou, A.; Campos-Herrera, R. Insecticidal Effect of Entomopathogenic Nematodes and the Cell-Free Supernatant from Their Symbiotic Bacteria against Philaenus spumarius (Hemiptera: Aphrophoridae) Nymphs. Insects 2021, 12, 448. https://doi.
Entomopathogenic nematodes (EPNs) are excellent biological control agents. Although traditionally EPN application targeted belowground insects, their aboveground use can be supported if combined with adjuvants. We hypothesized that EPN infective juveniles (IJs) could be combined with plant-based oils as adjuvants, without decreasing their efficacy against insect larvae under various scenarios. Specifically, our objectives were to evaluate the activity of Steinernema colombiense (Nematoda: Steinernematidae) when mixed with two plant-based oils (coconut and olive oils) and maintained at different temperatures and times, or combined with entomopathogenic fungi. First, we evaluated how these oils affected IJ survival and virulence against last instar Galleria mellonella (Lepidoptera: Pyralidae) larvae when maintained at five different temperatures (4, 8, 14, 20, and 24°C) and five incubation times (1, 3, 7, 14, and 21 days), using water as control treatment. Second, we evaluated virulence when combined with these two oils as well as with water (control) and combined with the entomopathogenic fungi (EPF), Beauveria bassiana (Hypocreales: Clavicipitaceae). Infective juvenile survival was higher in coconut than olive oil and water mixtures up to 7 days at 4°C. Conversely, olive oil supported higher larval mortality than coconut oil at 4 to 20°C and 14 days. Similarly, the number of days needed to kill insect larvae increased at extreme temperatures (4 and 24°C) after 14 days. Finally, the EPN + EPF combination showed an additive effect compared to EPN and EPF single treatments. Our findings indicate that our plant-based oil mixtures maintain viable IJs at moderate temperatures and up to 7 to 14 days, and can be used in single EPN mixtures or combined with EPF.
Viticulture is a key sector of the agricultural economy of the main wine-producing countries, e.g. Italy, France, Spain and the USA, but is also one of the main users of phytosanitary products and mechanization. Over the last 15 years, numerous studies of the effect of viticultural practices on soil quality have evidenced strong impacts on soil physical, chemical and biological quality. However, to date a global analysis providing a comprehensive overview of the ecotoxicological impacts of viticultural practices on soil biological quality is missing. Here, we conducted a meta-analysis of the literature in order to rank viticultural production systems and practices according to their impact on soil biodiversity and functioning in the context of the agro-ecological transition. We screened about one hundred articles and gathered data on more than 50 viticultural factors and 230 soil biological parameters. The results show that soil microorganisms are threefold to fourfold higher under organic viticulture than under conventional viticulture in terms of biomass, respiration and activity; and that biodynamic viticulture shows a similar trend than organic viticulture. Tillage, the absence of soil cover and mineral fertilization are significantly deleterious to the whole soil biodiversity, whereas cover crops, organic fertilizers and addition of grapevine pruning wood are beneficial. Pesticides—especially herbicides—have an ecotoxicological impact on soil organisms, notably on nematodes with losses of up to two-thirds of individuals. The pivotal role of biodiversity in soil functions implies that this degradation will have substantial consequences on the ecological and agronomical services provided by the soil for vine production. On this basis, we propose a potentially more agro-ecological and sustainable vine production system based on the more virtuous practices.
Viticulture and winemaking are important socioeconomic sectors in many European regions. Climate plays a vital role in the terroir of a given wine region, as it strongly controls canopy microclimate, vine growth, vine physiology, yield, and berry composition, which together determine wine attributes and typicity. New challenges are, however, predicted to arise from climate change, as grapevine cultivation is deeply dependent on weather and climate conditions. Changes in viticultural suitability over the last decades, for viticulture in general or the use of specific varieties, have already been reported for many wine regions. Despite spatially heterogeneous impacts, climate change is anticipated to exacerbate these recent trends on suitability for wine production. These shifts may reshape the geographical distribution of wine regions, while wine typicity may also be threatened in most cases. Changing climates will thereby urge for the implementation of timely, suitable, and cost-effective adaptation strategies, which should also be thoroughly planned and tuned to local conditions for an effective risk reduction. Although the potential of the different adaptation options is not yet fully investigated, deserving further research activities, their adoption will be of utmost relevance to maintain the socioeconomic and environmental sustainability of the highly valued viticulture and winemaking sector in Europe.
The vine mealybug, Planococcus ficus Signoret (Hemiptera: Pseudococcidae), is a key insect pest of South African grapevine. The ability of mealybugs to avoid or resist the action of chemical pesticides has led to the investigation of alternative control methods, such as the application of entomopathogenic nematodes (EPNs). However, EPN application faces challenges, due to the maladaptation of EPN species to above-ground conditions. In this study, the ability of adjuvants to improve the control of P. ficus in grapevine using an indigenous nematode species, Steinernema yirgalemense, was investigated. A trial was performed to assess EPN survival on grapevine foliage, when applied in the morning (high humidity / low temperature) compared with in the afternoon (high temperature / low humidity). In a semi-field trial, the combination of adjuvants Zeba® and Nu-Film-P® resulted in 66% control of P. ficus after 48 h, compared to the use of Zeba® alone (43%), and EPNs alone (28%). Additionally, lower concentrations of EPNs showed predictably lower mortality rates of P. ficus. Significantly, higher EPN survival was recorded at each time interval in the morning, compared with the corresponding interval in the afternoon. This study demonstrates the ability of S. yirgalemense, when applied with adjuvants and at an appropriate time of day, to control P. ficus on grapevine, under semi-field conditions.
The European grapevine moth, Lobesia botrana Den. & Schiff. (Lepidoptera: Tortricidae) and the gray rot fungus (Botrytis cinerea) are two important factors that cause elevated losses of productivity in vineyards globally. The European grapevine moth is one of the most important pests in vineyards around the world, not only because of its direct damage to crops, but also due to its association with the gray rot fungus; both organisms are highly detrimental to the same crop. Currently, there is no effective, economic, and eco-friendly technique that can be applied for the control of both agents. On the other hand, Metarhizium anisopliae belongs to a diverse group of entomopathogenic fungi of asexual reproduction and global distribution. Several Metarhizium isolates have been discovered causing large epizootics to over 300 insects’ species worldwide. In this study, a simple design was conducted to evaluate the potential of native M. anisopliae isolates as one of biological control agents against L. botrana and as possible growth inhibitors to B. cinerea. Entomopathogenic fungal strains were isolated from arid soils under vine (Vitis vinifera) culture. Results suggest that the three entomopathogenic strains (CEP413, CEP589, and CEP591) were highly efficient in controlling larval and pupal stages of L. botrana, with mortality rates ranging from 81 to 98% (within 4–6 days). Also, growth inhibition over B. cinerea strains resulted in percentages ranged from 47 to 64%. Finally, the compatibility of the entomopathogenic strains, with seven commercial fungicides, was evaluated. The potential of the entomopathogenic fungal strains to act as control agents is discussed.
The vine mealybug (Planococcusficus) is regarded as a key mealybug pest of grapevines in South Africa, with entomopathogenic nematodes (EPNs) being touted as a potential alternative to chemical control, although their vulnerability to above-ground environmental conditions has limited their use. In this study, tests were conducted to assess the ability of adjuvants to increase the deposition of S. yirgalemense on grapevine leaves. The combination of Nu-Film-P® and Zeba® resulted in significantly more infective juveniles (30) being deposited per 4 cm² leaf disc than with either the control (14.8), or with Nu-Film-P® (23.3), although not significantly more than with Zeba® alone (29.2). The ability of S. yirgalemense, in conjunction with the two adjuvants, to control P. ficus on grapevine foliage was then assessed under controlled conditions. The application of S. yirgalemense with both Zeba® and Nu-Film-P® to P. ficus on leaf discs in a growth chamber resulted in 84% mortality, significantly greater than that attained by the application of S. yirgalemense with either Zeba® (47%), or water alone (26%). Similar results were observed in a glasshouse trial, in which the combination of S. yirgalemense, Zeba® and Nu-Film-P® offered 88% control of P. ficus on leaf discs hung on potted vines, compared with the control that was achieved with S. yirgalemense with either Zeba® (56%) or water alone (30%). This study demonstrates the potential of a combination of S. yirgalemense with adjuvants to give significant control of P. ficus on grapevine foliage, compared with using EPNs alone.
The wheat stem sawfly, (Cephus cinctus Norton) Hymenoptera: Cephidae, has been a
major pest of winter wheat and barley in the northern Great Plains for more than 100 years.
The insect's cryptic nature and lack of safe chemical control options make the wheat stem
sawfly (WSS) difficult to manage; thus, biological control offers the best hope for sustainable
management of WSS. Entomopathogenic nematodes (EPNs) have been used successfully
against other above-ground insect pests, and adding adjuvants to sprays containing EPNs
has been shown to improve their effectiveness. We tested the hypothesis that adding chemical
adjuvants to sprays containing EPNs will increase the ability of EPNs to enter wheat
stems and kill diapausing WSS larvae. This is the first study to test the ability of EPNs to
infect the WSS, C. cinctus, and test EPNs combined with adjuvants against C. cinctus in
both the laboratory and the field. Infection assays showed that three different species of
EPNs caused 60±100% mortality to WSS larvae. Adding Penterra, Silwet L-77, Sunspray
11N, or Syl-Tac to solutions containing EPNs resulted in higher WSS mortality than solutions
made with water alone. Field tests showed that sprays containing S. feltiae added to
0.1% Penterra increased WSS mortality up to 29.1%. These results indicate a novel control
method for WSS, and represent a significant advancement in the biological control of this
persistent insect pest.
No species lives on earth forever. Knowing when and why species go extinct is crucial for a complete understanding of the consequences of anthropogenic activity, and its impact on ecosystem functioning. Even though soil biota play a key role in maintaining the functioning of ecosystems, the vast majority of existing studies focus on aboveground organisms. Many questions about the fate of belowground organisms remain open, so the combined effort of theorists and applied ecologists is needed in the ongoing development of soil extinction ecology.
The development and use of entomopathogens as classical, conservation and augmentative biological control agents have included a number of successes and some setbacks in the past 15 years. In this forum paper we present current information on development, use and future directions of insect-specific viruses, bacteria, fungi and nematodes as components of integrated pest management strategies for control of arthropod pests of crops, forests, urban habitats, and insects of medical and veterinary importance.
In South Africa, the most common method of mealybug control has been the use of chemical insecticides.
Entomopathogenic nematodes (EPNs) of the of the families Heterorhabditidae and Steinernematidae
potentially can be used within an integrated pest management scheme to control Planococcus ficus, the vine
mealybug, which occurs on all parts of grapevine, including the roots. When Steinernema yirgalemense
was applied to the soil of two vineyards with P. ficus, contained in pierced Eppendorf tubes, buried at
a depth of 15 cm in the soil, mortalities of up to 50% were obtained after 48 h. The persistence of S.
yirgalemense, measured using codling moth larval mortality was found to be zero in one vineyard, while
in the other it was 70%, 12 weeks after application. Tests were conducted to establish the production of
scavenger deterrent factors by H. zealandica and S. yirgalemense. Of the cadavers that were presented
six days after nematode infection, 49% of the H. zealandica- and 60% of the S. yirgalemense-infected
cadavers were left intact. Olfactometry tests indicated a significant difference concerning the number of
S. yirgalemense infective juveniles (IJs) that were attracted to damaged Vitis vinifera roots and P. ficus,
indicating active movement of the IJs and the attractive ability of organic compounds produced by the
roots. This study shows that EPNs, and specifically S. yirgalemense, have promising potential as biological
control agents for the control of P. ficus soil populations, and investigates some influential factors affecting
EPNs as biocontrol agents in the agro-ecosystem.
We present the results of studies in organic vineyards in Mendocino and Sonoma counties, California, in an effort to systematize the emerging lessons from our experience on vineyard biodiversity enhancement for ecologically-based pest management. In the Mendocino study, a vegetational corridor connected to a riparian forest channeled insect biodiversity from surrounding habitats into the vineyard, thus overcoming the restricted spatial limits to which the positive influence of adjacent vegetation on vineyard pest dynamics is usually confined. In addition, summer cover crops substantially enhanced biological control of leafhoppers and thrips, by breaking the virtual monoculture that vineyards become in the summer after winter cover crops dry out or are plowed under. In the Sonoma vineyard, an island of flowering shrubs and herbs provided season-long flower resources and alternate preys/hosts for natural enemies, which slowly built up in the adjacent vineyard. The island acted as a push-pull system for natural enemies, enhancing their activity but confining them mostly to the adjacent vine rows. Planting strips of summer cover crops could be a strategy to overcome the push effect of the island.
To determine the risk winery waste poses for the spread of Lobesia botrana (Denis & Schiffermüller) (Lepidoptera: Tortricidae) in California, we evaluated the survival of larvae in artificially infested grape clusters (Vitis vinifera L.) processed for wine making. The trial consisted of five treatments: whole cluster pressing to 1 bar (100,000 Pa); whole cluster pressing to 2 bars (200,000 Pa); destemming and berry pressing to 1 bar; destemming and berry pressing to 2 bars; and control. Each treatment was replicated with the following five winegrape varieties: Chardonnay, Sauvignon Blanc, Gewürztraminer, Yellow Muscat, and Cabernet Sauvignon. All winery waste was inspected for larval survival. No live larvae were recovered from any of the treatments in all five varieties; therefore, the hypothesis that green winery waste contributes to the spread of L. botrana was rejected.
Larvae of Lobesia botrana, the grape berry moth, increase the severity of gray mold on grapes (cv. Sauvignon). The role of larval wounds on the colonization of immature berries by Botrytis cinerea was studied with scanning electron microscopy. On vineyard berries, emergence of conidiophores is favored at the entrance of larval galleries, and fungal development is enhanced at superficial wound sites. A greenhouse trial showed that conidia were introduced inside larval galleries by larvae externally contaminated by the fungus. The germination of conidia and resulting mycelial colonization followed on the inner surfaces of galleries. The role of transport of viable conidia by larvae was also assessed under field conditions. On immature berries, the artificial supply of viable conidia on the cuticle of second-generation larvae caused a significant increase in the percentage of larval injuries infected by B. cinerea (20% for clusters with normal compactness and 10% for thinned clusters after 15 days of larval presence). As for damage to ripe berries, third-generation larvae carrying viable conidia caused a 2.4% increase in disease severity at harvest as compared with larvae carrying dead conidia.
This study explores the influence of a selection of adjuvants and of three different nozzle sizes on the foliar application of entomopathogenic nematodes (EPNs). Two EPN species were studied: Steinernema feltiae and Steinernema carpocapsae. Aviability test of EPNs suspended in different solutions of adjuvants showed that all selected alcohol ethoxylates and an alkyl polysaccharide have an immobilising effect on the selected nematode species. In a sedimentation test, xanthan gum proved to be the only adjuvant in a broad selection, capable of delaying sedimentation of EPNs in suspension. Without xanthan gum, sedimentation of S. carpocapsae and S. feltiae was noticeable after 20 and 10 minutes, respectively. When xanthan gum (0.3 g/L) was added to the suspension, no signs of sedimentation were noticed after 20 minutes with both EPN species. An ISO 02 flat fan nozzle can clog when spraying S. carpocapsae. A deposition test determined that an ISO 04 standard flat fan nozzle provides a higher relative deposition on cauliflower leaves and is therefore a better nozzle choice than the bigger ISO 08 standard flat fan nozzle for spraying S. carpocapsae. The addition of a spreading agent improved the deposition of S. carpocapsae. Adding xanthan gum to the EPN-spreading agent mixtures did not further improve deposition.
Background:
Steinernema carpocapsae Weiser, an entomopathogenic nematode (EPN), is a potential biological control agent for the cabbage moth (Mamestra brassicae L.). This research aimed to identify a suitable spray application technique, and to determine whether yeast extract added to an EPN spray has an attracting and/or a feeding stimulant effect on M. brassicae. The biological control capabilities of EPN against this pest were examined in the field.
Results:
Good coverage of the underside of cauliflower leaves, the habitat of young instar larvae (L1-L4) of M. brassicae was obtained using different spray boom configurations with vertical extensions that carried underleaf spraying nozzles. One of the configurations was selected for field testing with an EPN spray. Brewer's yeast extract stimulated larval feeding on leaves, and increased the mortality of these larvae when exposed to EPN. The field trial showed that a spray application with S. carpocapsae, Addit and xanthan gum can effectively lower the numbers of cabbage heads damaged by M. brassicae. Brewer's yeast extract did not significantly increase this field performance of EPN.
Conclusion:
Steinernema carpocapsae, applied with an appropriate spray technique, can be used within biological control schemes as part of a resistance management programme for Bt.
Entomopathogenic nematodes (EPNs) have been utilized in classical, conservation, and augmentative biological control programs. The vast majority of applied research has focused on their potential as inundatively applied augmentative biological control agents. Extensive research over the past three decades has demonstrated both their successes and failures for control of insect pests of crops, ornamental plants, trees and lawn and turf. In this paper we present highlights of their development for control of insect pests above and below ground. The target insects include those from foliar, soil surface, cryptic and subterranean habitats. Advances in mass-production and formulation technology of EPNs, the discovery of numerous efficacious isolates/strains, and the desirability of reducing pesticide usage have resulted in a surge of commercial use and development of EPNs. Commercially produced EPNs are currently in use for control of scarab larvae in lawns and turf, fungus gnats in mushroom production, invasive mole crickets in lawn and turf, black vine weevil in nursery plants, and Diaprepes root weevil in citrus in addition to other pest insects. However, demonstrated successful control of several other insects, often has not lead to capture of a significant share of the pesticide market for these pests.
Understanding the desiccation survival attributes of infective juveniles of entomopathogenic nematodes (EPN) of the genera Steinernema and Heterorhabditis, is central to evaluating the reality of enhancing the shelf-life and field persistence of commercial formulations. Early work on the structural and physiological aspects of desiccation survival focused on the role of the molted cuticle in controlling the rate of water loss and the importance of energy reserves, particularly neutral lipids. The accumulation of trehalose was also found to enhance desiccation survival. Isolation of natural populations that can survive harsh environments, such as deserts, indicated that some populations have enhanced abilities to survive desiccation. However, survival abilities of EPN are limited compared with those of some species of plant-parasitic nematodes inhabiting aerial parts of plants. Research on EPN stress tolerance has expanded on two main lines: i) to select strains of species, currently in use commercially, which have increased tolerance to environmental extremes; and ii) to utilize molecular information, including expressed sequence tags and genome sequence data, to determine the underlying genetic factors that control longevity and stress tolerance of EPN. However, given the inherent limitations of EPN survival ability, it is likely that improved formulation will be the major factor to enhance EPN longevity and, perhaps, increase the range of applications.
Production and application technology is critical for the success of entomopathogenic nematodes (EPNs) in biological control. Production approaches include in vivo, and in vitro methods (solid or liquid fermentation). For laboratory use and small scale field experiments, in vivo production of EPNs appears to be the appropriate method. In vivo production is also appropriate for niche markets and small growers where a lack of capital, scientific expertise or infrastructure cannot justify large investments into in vitro culture technology. In vitro technology is used when large scale production is needed at reasonable quality and cost. Infective juveniles of entomopathogenic nematodes are usually applied using various spray equipment and standard irrigation systems. Enhanced efficacy in EPN applications can be facilitated through improved delivery mechanisms (e.g., cadaver application) or optimization of spray equipment. Substantial progress has been made in recent years in developing EPN formulations, particularly for above ground applications, e.g., mixing EPNs with surfactants or polymers or with sprayable gels. Bait formulations and insect host cadavers can enhance EPN persistence and reduce the quantity of nematodes required per unit area. This review provides a summary and analysis of factors that affect production and application of EPNs and offers insights for their future in biological insect suppression.
Abstract. In this review, the impacts of climate change on Lepidoptera species and communities are
summarized, regarding already registered changes in case of individual species and assemblies, and
possible future effects. These include changes in abundance, distribution ranges (altitude above sea level,
geographical distribution), phenology (earlier or later flying, number of generations per year). The paper
also contains a short description of the observed impacts of single factors and conditions (temperature,
atmospheric CO2 concentration, drought, predators and parasitoids, UV-B radiation) affecting the life of
moths and butterflies, and recorded monitoring results of changes in the Lepidoptera communities of
some observed areas. The review is closed with some theoretical considerations concerning the
characteristics of “winner” species and also the features and conditions needed for a successful invasion,
conquest of new territories.
Keywords: butterflies, moths, abundance, distribution, phenology
False codling moth (FCM), Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae), is a priority pest on citrus, stone fruit, and table grapes. Current control focuses on the adult stage; however, each stage of the life cycle of the insect should be targeted. The potential of local biocontrol agents against FCM immature stages were investigated. Several entomopathogenic nematode (EPN) and entomopathogenic fungi (EPF) species were identified from soil samples collected from orchards and vineyards throughout the Western Cape province in South Africa. The eggs were proven to be susceptible (30–65%) to several EPN species, at 200 infective juveniles (IJs) per 50 µl. Xenorhabdus indica, the symbiotic bacterium of Steinernema yirgalemense Nguyen et al., caused significantly more mortality than the control. The EPNs were highly virulent against the FCM larvae, with S. yirgalemense causing 100% mortality in all trials. Metarhizium robertsii (78%), M. anisopliae (50%), and Beauveria bassiana (75%) caused high mortality in FCM larvae. The fully formed pupae were the most resistant of the immature stages, with the EPNs causing low mortality at 100 IJs per insect. As the FCM larvae were highly susceptible to S. yirgalemense and M. robertsii under laboratory conditions, they should be further tested, separately and in combination, in field conditions to illustrate the benefits of including them in a FCM‐IPM programme.
Viticulture is a valuable sector worldwide with an extraordinary socio-economic impact in Spain. Numerous pests and diseases threaten vineyards, and their management primarily relies on the use of conventional agrochemicals. The current paradigm of sustainability pursues the implementation of ecologically sound strategies in vineyard ecosystems. The use of cover crops is arising as an alternative with numerous benefits, including favoring above-belowground biodiversity and the presence of beneficial soil organisms such as the entomopathogenic nematodes (EPNs). We hypothesized that the use of specific cover crops in vineyards might enhance the natural occurrence and activity of EPNs by modulating the assemblage with associated organisms. We performed the experiments in an ongoing experimental vineyard (Vitis vinifera var Tempranillo, clon RJ-26, rootstock ‘110-Richter’) located in Logroño (Spain), drove with different soil management systems (three replicates each): conventional tillage practice and the cover crops (i) seeded with Bromus catharticus (Poaceae), (ii) flower-driven, and (iii) spontaneous. We took four soil composite samples per plot (n = 48 per sampling time) late spring and early autumn in two consecutive years (2017 and 2018). By using species-specific primers/probes qPCR sets, we screened for the presence and abundance of eight EPNs species and 12 related soil organisms: six nematophagous fungi, four free-living nematodes, and two ectoparasitic bacteria. Additionally, we assessed the EPN activity by the traditional insect-bait method. Overall, we recorded higher EPN numbers or activity rates on cover crops than on bare soils. However, some of the results were divergent among no-till treatments. We observed not only higher EPN abundance and activity on spontaneous covers but lower numbers of antagonistic organisms, particularly endoparasitic nematophagous fungi. Thus, according to our results, the use of spontaneous covers could be the most promising strategy to support the conservation biological control service provided by the naturally occurring EPN species in vineyards, plus with a low cost for the sector.
The effects of secondary metabolites produced by the following symbiotic bacteria, Xenorhabdus szentirmaii, X. nematophila, X. bovienii, X. cabanillasii, Photorhabdus luminescens and P. temperata, associated with entomopathogenic nematodes, were investigated against various developmental stages of Tetranychus urticae (Acari: Tetranychidae) using cell-free bacterial supernatants in Petri dishes. In addition, the effects of the most active bacterial supernatant(s) found in Petri dish experiments were tested on T. urticae in pot experiments. All studies were conducted at 25 ± 1 °C temperature, 70 ± 5% relative humidity and a light cycle of 16 h in a climate room. The result of the Petri dish experiments showed that the supernatants had little or no effect on the egg stage, as less than 4% mortality was recorded. Depending on the bacterial supernatant, mortality in the other stages was 46–97% for larvae, 30–96% for protonymphs, 41–92% for deutonymphs, 92–100% for adult males and 46–93% for adult females. Control mortalities ranged from 1−7% for larvae, 2–9% for protonymphs, 4–10% for deutonymphs, 6–10% for adult males and 4–8% for adult females. Among supernatants tested, X. szentirmaii and X. nematophila were the most efficacious with mortality greater than 90% on the mobile stages of T. urticae. According to the results from pot experiments, the supernatants of X. szentirmaii and X. nematophila, singularly and in combination, significantly reduced the T. urticae population. However, the mixture of X. szentirmaii and X. nematophila supernatants did not increase efficiency to reduce T. urticae population compared to each supernatant alone. Further studies are warranted to find the active compound(s) in the supernatants of X. szentirmaii or and X. nematophila and assess whether the supernatant(s) has the potential of being a practical and economical control agent for T. urticae.
Pesticides are needed to maintain high production in the vineyard area of La Rioja (Spain), and monitoring their spatial distribution is a priority for preserving the quality of natural resources. Accordingly, the purpose of this work was to conduct a study to evaluate the presence and seasonal distribution of herbicide and insecticide residues in ground and surface waters in this region. The monitoring network comprised 12 surface waters and 78 groundwaters, covering the three subareas (63,593 ha) into which the vineyard region is divided. The quality of natural waters was examined through the analysis of twenty-two herbicides, eight of their main degradation products, and eight insecticides. Pesticides were extracted by solid-phase extraction, and analysed by gas chromatography–mass spectrometry or by liquid-chromatography-mass spectrometry. The results reveal the presence of most of the herbicides and insecticides included in the study in one or more of the samples collected during the four campaigns. The herbicide terbuthylazine and its metabolite desethylterbuthylazine were the compounds more frequently detected (present in > 65% of the samples across all the campaigns). Other compounds detected in > 50% of the samples in one sampling campaign were the herbicides fluometuron, metolachlor, alachlor and ethofumesate. Insecticides were present in a small number of samples, with only pirimicarb being detected in > 25% of the samples in March and June campaigns. The results reveal that the sum of compounds detected (mainly herbicides) was higher than 0.5 μg L− 1 in > 50% of the samples, especially in the campaigns with the highest application of these compounds. A possible recovery of the quality of the waters was detected outside the periods of crop cultivation, although more monitoring programmes are needed to confirm this trend with a view to preventing and/or maintaining the sustainability of natural resources.
Entomopathogenic nematodes (EPNs) and their bacterial partners are well-studied insect pathogens, and their persistence in soils is one of the key parameters for successful use as biological control agents in agroecosystems. Free-living bacteriophagous nematodes (FLBNs) in the genus Oscheius, often found in soils, can interfere in EPN reproduction when exposed to live insect larvae. Both groups of nematodes can act as facultative scavengers as a survival strategy. Our hypothesis was that EPNs will reproduce in insect cadavers under FLBN presence, but their reproductive capacity will be severely limited when competing with other scavengers for the same niche. We explored the outcome of EPN - Oscheius interaction by using freeze-killed larvae of Galleria mellonella. The differential reproduction ability of two EPN species (Steinernema kraussei and Heterorhabditis megidis), single applied or combined with two FLBNs (Oscheius onirici or Oscheius tipulae), was evaluated under two different infective juvenile (IJ) pressure: low (3IJs/host) and high (20IJs/host). EPNs were able to reproduce in insect cadavers even in the presence of potential scavenger competitors, although EPN progeny was lower than that recorded in live larvae. Hence, when a highly susceptible host is available, exploiting cadavers by EPN might limit the adaptive advantage conferred by the bacteria partner, and might result in an important trade-off on long-term persistence. Contrary to our hypothesis, for most of the combinations, there were not evidences of competitive relationship between both groups of nematodes in freeze-killed larvae, probably because their interactions are subject to interference by the microbial growth inside the dead host. Indeed, evidences of possible beneficial effect of FLBN presence were observed in certain EPN-FLBN treatments compared with single EPN exposure, highlighting the species-specific and context dependency of these multitrophic interactions occurring in the soil.
Domestication and improvement of crop plants and animals have been part of agriculture for thousands of years, and many agricultural systems are therefore artificial. Genetic manipulation of other beneficial arthropods, such as silkworms and honeybees, has been conducted for hundreds of years (Hoy, 1990; Yokoyama, 1973). As in crop breeding, four potential genetic–manipulation strategies exist: artificial selection, hybridization (use of heterosis), mutation, and recombinant DNA techniques.
Entomopathogenic nematodes (EPN) of the genera Steinernema and Heterorhabditis are widely used in inundative biological pest control programmes. It has long been recognised that increased understanding of the ecology of EPN is important for better predictions of field performance and environmental risk (Ehlers & Hokkanen, 1996; Gaugler, Lewis, & Stuart, 1997). Increasingly, EPN are also finding a place as model organisms for fundamental studies in behavioural ecology and evolutionary biology (Campos-Herrera, Barbercheck, Hoy, & Stock, 2012). In this chapter, I consider the fate of EPN used in biocontrol, focussing largely on inundative application to soil. The aim is to provide an overview of the transformation of a biotechnological product to an ecological entity, rather than a review of this rather broad topic. There are already several extensive reviews relevant to the subject, including EPN behaviour and their fate in soil (e.g. Griffin, 2012; Kaya, 2002; Lewis, Campbell, Griffin, Kaya, & Peters, 2006; Stuart, Barbercheck, Grewal, Taylor, & Hoy, 2006; see also Chap. 4). It should be noted that, while the concept of this chapter is to follow the fate of commercially produced EPN when applied to soil, many of the laboratory studies cited have used nematodes produced in insects rather than taken from commercial formulations.
Nematodes are among the most abundant organisms on Earth, as they exist in almost every possible habitat and ecosystem (Bernard, 1992; De Ley, 2006; Ettema, 1998; Powers et al. 2009). Indeed, these organisms can be found in aquatic (marine and fresh water) and terrestrial ecosystems ranging from the tropics to the poles and from the highest to the lowest of elevations. Furthermore, nematodes have exploited a wide range of ecological niches encompassing free–living and parasitic species. Parasites have received the most attention and have been the subject of extensive research because of the damage they cause to crops, livestock, and humans (Anderson, 2000; Norton, 1978; Poinar, 1983; Stirling, Poinar, & Jansson, 1988; Wallace, 1963; Zuckerman & Rhode, 1981). However, several parasitic species are considered beneficial organisms to humans as they can be used as control agents of pests that are of agriculture, forestry or health importance (Bedding, Akhurst, & Kaya, 1993; Gaugler & Kaya, 1990; Grewal, Grewal, & Adams, 2003; Petersen, 1985; Poinar; Stock & Hunt, 2005; Wilson & Gaugler, 2000; Wilson, Glen, & George, 1993).
The efficacy of aboveground applications of entomopathogenic nematodes (Heterorhabditis spp. and Steinernema spp.) can be severely limited by the nematode's susceptibility to UV radiation and desiccation. The lesser peachtree borer, Synanthedon pictipes, is a major pest of stone fruit; larvae attack trees aboveground by tunneling into the trunk and scaffold limbs. In previous research, Steinernema carpocapsae, caused high levels of S. pictipes mortality when a sprayable fire gel (Barricade®) was applied on top of the nematode application as a protectant. One drawback to the approach is that two applications must be made (first nematodes are applied followed by the fire gel); furthermore, the previous experiments did not compare nematode application to the existing standard chemical insecticide. Therefore, the objectives of this study were to (1) determine if a diluted rate of fire gel can protect nematodes when applied as a single spray, and (2) compare the efficacy of nematode applications with the chemical insecticide, chlorpyrifos. The experiment was conducted in a peach orchard in Quincy, Florida in 2013 and 2014. Treatments included: (1) chlorpyrifos, (2) S. carpocapsae applied in aqueous suspension only or (3) with a full rate (approximately 4% applied separately) or (4) 2% Barricade® (applied with nematodes in a single spray), and (5) a non-treated control. The treatments were applied post-harvest (in the fall) to S. pictipes-infested bark wounds; S. pictipes survival was assessed 8 (2013) or 14 (2014) d post-application. In 2013, chlorpyrifos and nematodes with Barricade® at 2% or the full rate reduced S. pictipes survival relative to the non-treated control and nematodes without Barricade®. In 2014, nematodes applied with 2% Barricade® was the only treatment that reduced S. pictipes survival. We conclude that S. carpocapsae and Barricade® can be applied as a single spray, and in our experiments the treatment was at least as effective as the chemical standard.
The grape berry moths Lobesia botrana and Eupoecilia ambiguella are the two main grape pest species. Their occurrence, bionomics, economic importance, prognosis and prediction of infestation, are discussed. The changes in control methods, from predominantly chemical control to the more selective procedures of biological and biotechnical control, are reviewed. -J.W.Cooper
Field efficacy and persistence of Heterorhabditis zealandica strain X1 and Heterorhabditis bacteriophora strain GPS11 applied at different times for the control of the grape root borer, Vitacea polistiformis were evaluated from 2001 to 2003 in two vineyards in Ohio and one in Georgia and from 2005 to 2007 in two vineyards in Ohio. Pheromone trapping and pupal case surveys were used to confirm the presence of borers in the vineyards. Nematode applications were targeted at the larval stages of the grape root borer. Percent control based on the number of emerging adults in Ohio ranged from 55% to 92% and in Georgia from 55% to 78%. Overall no significant differences were found in the numbers or timings of nematode application indicating effective control of all GRB instars and a broad window of opportunity for the application of nematodes. The ability of H. zealandica to persist in the soil profile for a period of 1year was minimal in Ohio and none in Georgia. In contrast, H. bacteriophora persistence in Ohio was positive for all treatments up to 1year post-treatment and in one case up to 21months post-treatment. These studies demonstrate the potential of H. bacteriophora strain GPS11 for long-term conservation approach in vineyards for the management of the grape root borer.
The infective juvenile is a free-living stage of entomopathogenic nematodes (Rhabditida: Heterorhabditidae and Steinernematidae) that serves three main functions: dispersal, host finding, and survival under environmental conditions detrimental to other life stages. Here, we summarize the research on the physiology, genetics, and molecular biology of chemoreception, thermobiosis, and anhydrobiosis in the infective juveniles. Chemoreception studies in Heterorhabditis bacteriophora indicate that the adoption of the parasitic mode of life is associated with a reduced sensitivity to volatile by-products of bacterial metabolism and an increased sensitivity towards long-chain alcohols and other insect-specific volatiles. Thermobiosis and anhydrobiosis studies reveal that entomopathogenic nematode infective juveniles use a global stress tolerance response that may be triggered during acclimation to a novel temperature or desiccation regime. Once this global stress response is induced, the nematodes acquire resistance to a multitude of factors including cold, heat, desiccation, ultraviolet radiation, and pH. Physiological mechanisms manifested by entomopathogenic nematode infective juveniles during survival under cold or warm conditions include the alteration in the proportion of saturated and unsaturated fatty acids, alterations in the activity of metabolic enzymes, synthesis of novel isozymes, sugars, and polyols including trehalose and glucose, and heat-shock proteins. It is apparent that thermal niche breadths of entomopathogenic nematodes are conserved, but they can be altered through genetic selection at constant temperatures. Infective juveniles can undergo anhydrobiosis within and outside the host cadaver. The physiological mechanisms to undergo anhydrobiosis include the synthesis of polyols, sugars such as trehalose, alterations in the fatty acid composition, and the synthesis of several low molecular weight proteins. With the significant progress made in unraveling the steps involved in olfactory signaling in Caenorhabditis elegans, homology-based approaches are now being used to isolate chemosensory genes in H. bacteriophora. Using a variety of cloning techniques and subtractive hybridization, several genes involved in chemoreception, heat tolerance, and anhydrobiosis of entomopathogenic nematodes have been isolated. These discoveries together with the availability of new molecular and genomic tools serve as a solid platform for the improvement of biological control potential of entomopathogenic nematodes.
Increasing resistance to chemical insecticides in field populations of the diamondback moth (Plutella xylostella) has stimulated research on alternative control measures. The entomopathogenic nematode Steinernema carpocapsae may be one such alternative, particularly against the third larval instar of P. xylostella. The LC50 for the second instar is 38, the third 13 and the fourth 22 nematodes/larva. Plutella xylostella pupae were not affected by the nematodes, although mortality in leaf disk bioassays after application of nematodes in water seldom surpassed 50%. Therefore, additives were tested to improve nematode performance. Only Triton X-100 (0.3%) caused phytotoxic effects. The addition of xanthan gum or potassium alginate resulted in a two-fold increase of insect mortality at 80% relative humidity (RH) and a five-fold increase at 60% RH. Mixtures of 0.3% xanthan or alginate with 0.3% surfactants further improved efficacy. In water the LT50 for S. carpocapsae against P. xylostella larvae was > 40 h. Using a mixture of 0.3% xanthan or 0.3% alginate with 0.3% surfactant, the LT50 was reduced to < 25 h.