Arthropod-Plant Interactions

The aim of this study focussed on identifying chemical compounds (wood extractives) using different solvents, as well as their performance as a wood preservative against subterranean termites, Coptotermes gestroi (Wasmann) attack. The source of wood extractives was from Palaquium gutta (Hook.f.) Baillon and Pometia pinnata J.R. Forster & J.G. Forster, heartwood extracted with different solvents; absolute ethanol (EtOH), absolute methanol (MeOH) and petroleum ether (PETETHR). Compound identification was performed under Gas Chromatography and Mass Spectrometry (GC–MS). Besides that, the efficacy of extracts from both timber species was also assessed in various bioassays (antitermitic, repellent, antifeedant & test of wood extractives applied to Hevea brasiliensis). A total of 20 and 22 compounds were identified from P. gutta and P. pinnata heartwood extracts, respectively. Decalactone, isobornyl isobutanoate, carvacrol, rosifoliol, incensole acetate, citronellyl pentanoate, allyl cinnamate, thujic acid, cubebolo, citronellol, manool, neoisopulegol, widdrol and methyl decyl ketone were among the bioactive compounds of varying proportions among the studied timbers. The heartwood extracts from both timber species with MeOH solvent had a significantly lower percentage of paper consumption and higher percentage of feeding inhibition and repellent activity, followed by EtOH and PETETHR. Both timber species extracts had the potential to be developed as a new natural bio preservative in wood industries.

Plants live in association with a multitude of microorganisms, some of which may improve the plant’s defense toward herbivores. In a previous study, we showed that Metarhizium brunneum, a fungus mostly known as an insect pathogen, can associate with cabbage roots and prime an increased myrosinase activity upon attack by Plutella xylostella larvae. Here, we ask whether another Metarhizium species, M. robertsii, also primes plant defense and whether this involves leaf glucosinolate content in addition to myrosinase activity. In addition, we tested whether priming reverses after removal of larvae. M. robertsii established and could be reisolated from roots at the end of the experiment, 43 days after inoculation. Before larval herbivory, leaf glucosinolate content and myrosinase activity did not differ between fungal-inoculated and control plants. Immediately after herbivory, in contrast, both the glucosinolate content and myrosinase activity were higher in inoculated plants than in control plants and less leaf material was consumed of the inoculated plants. Twenty-four hours after herbivory, glucosinolates, and myrosinase activity had decreased again to levels like before herbivory. Total biomass and shoot–root ratio were not affected by M. robertsii colonization. In conclusion, Metarhizium fungi can associate with Brassica roots and prime above-ground glucosinolate content and myrosinase activity. The increased defense levels were down-regulated 24 h after herbivory. Root-associated Metarhizium species may thus affect above-ground herbivores indirectly by host plant priming, in addition to their well-known direct effects as insect pathogens.

Conventional agriculture has negative impacts on the ecosystems while ecological intensification can ameliorate these effects by enhancing ecological processes. Arbuscular mycorrhizal fungi (AMF) are plant root symbionts that improve access to soil nutrients affecting plant growth and biotic interactions. Agricultural managements differentially affect AMF communities, but how these changes feedback on aboveground plant interactions remains poorly studied. Lettuce (Lactuca sativa) is a common crop severely attacked by Liriomyza huidobrensis (Diptera: Agromizydae), a polyphagous leafminer that has developed resistance to various pesticides, for which managing plant defenses and tolerance represents a feasible option to regulate populations. The aim of this study was to investigate if AMF communities from ecological and conventional management produce differential effects on mycorrhizal interaction, tissue phosphorus content and growth of lettuce plants and on L. huidobrensis oviposition preference. In greenhouse, we compared the effects of soils from farms with conventional and ecological managements from central Argentina on lettuce plants, and exposed them to L. huidobrensis mated females. Mycorrhizal colonization was higher with AMF from ecological than conventional treatments, although plant biomass was lower in treatments with AMF than with sterile soils (Strl), or with soil microorganisms without AMF (MO), in both managements. Phosphorus content was significantly higher in plants with MO and AMF in comparison to Strl, with no difference between managements. Plants grown with AMF from ecological management soils were less attacked by leafminers. Also, the insect preferred to oviposit on plants with higher aerial biomass, and this preference increased in plants with lower P content.

Herbivorous insects from diverse feeding guild cause defoliation with different intensity and dissimilar tissue effects. We studied the effects on water relations and morpho-structural and hydraulic traits of Prunus avium leaves caused by two different patterns of artificial herbivory (the window feeding and cut treatments) that mimic the effect of insects such as Caliroa cerasi and lepidopteran larvae. The cut treatment resulted in higher leaf dry mass per area and leaf hydraulic conductance in the remaining tissue in relation to the window feeding treatment and the control. The window feeding treatment increased the tissue elasticity and decrease the stomatal conductance. Although each herbivory pattern affected to different leaf traits, all changes were on traits relevant to drought resistance. These results contribute to improve our understanding on plant–herbivore interactions.

Plant quality can shape plant–insect interactions and plant secondary metabolites are known to play an influential role in mediating these interactions. Cannabinoids are a group of terpenophenolic compounds in Cannabis that have demonstrated negative effects on insect herbivores, yet specific mechanisms are currently not well understood. Insects can modulate their rate of growth, food intake, or production of frass (i.e., insect feces) to mitigate consumption of a diet with poor nutritional quality. Detoxification and nutritional enzymes are essential in performing these functions. To test how cannabinoids impact insect performance and enzymatic activity, we performed no-choice feeding bioassays on fall armyworm (Spodoptera frugiperda) with artificial diet spiked with different concentrations of CBD and measured fall armyworm growth, consumption, and frass production and analyzed detoxification and nutritional enzyme activities. We found that as CBD concentration increased fall armyworm growth and consumption decreased, but found no impact on digestibility or conversion efficiencies. Results from the enzymatic assays varied, but CYP450 and protease activity decreased, while glucosidase activity increased, as CBD concentration increased. Relationships among enzyme activities suggest that a reduction in protease activity might limit a detoxification response, by limiting amino acid availability needed for detoxification enzyme production, even though energy collection activity, via increased glucosidase activity, occurred. These outcomes suggest specific mechanisms by which CBD has a negative influence on insect herbivore performance.

Plant-animal interactions and the plant chemical defence systems are a keystone of ecology and of particular interest because they fundamentally shape ecosystem functioning. Despite that, the factors and mechanisms driving the interactions between insectivorous predators and plants, via herbivore-induced plant volatiles—HIPVs remains to be fully understood. Insectivorous birds and arthropods can use chemical cues provided by herbivore-damaged plants, yet the specific chemical defensive traits that are involved in the interactions with predators remain unknown for many plant species. In our experiments, we compared plant volatiles of English oak (Quercus robur) and Sessile oak (Quercus petraea) saplings treated with methyl jasmonate (MeJA). We studied how the MeJA-induced plant volatiles differ between these two closely related plant species, and how it influences higher trophic taxa (e.g., predation, associated arthropod communities). Using plasticine caterpillars, we assessed attractiveness of MeJA-treated oaks (vs. control untreated oaks) for predators. Overall, in both plant species, attack attempts were significantly higher on MeJA-treated saplings compared to control saplings. Birds were responsible for the majority of attack attempts, followed by ants and other arthropods. The mean total amount of volatiles emitted by MeJA-induced saplings differed among the experimental oak species over time and repeated applications of MeJA. MeJA application had no significant effect on the abundance of arthropods. However, the mean body size of individuals of different feeding guilds was affected by MeJA treatment both negatively and positively, depending on the specific feeding guild. Overall, our study concludes that (1) the application of MeJA led to increased attractiveness of oak saplings for insectivorous predators, including invertebrates and birds; (2) MeJA-treated oak saplings emitted eight specific compounds that were not detected in control saplings and two additional compounds that were emitted at 100-fold higher levels in MeJA-treated saplings compared to control saplings; and (3) the predation rate on artificial caterpillars did not significantly differ between oak species.

Poplars establish on alluvial bars within sand and gravel-bed rivers. Alluvial bars also provide particularly suitable habitats for the proliferation of ants. We hypothesized that ants, by modifying substrate structure and resource availability in fluvial habitats, positively influence poplar growth during its establishment stage. We conducted a preliminary nine-month ex situ greenhouse experiment with one ant species (Lasius niger L.) and six different genotypes of poplar cuttings (Populus nigra L.), both collected on the Garonne River, SW France. Three main treatments: ‘P. nigra alone’, ‘P. nigra without ants and with ant food’ and ‘P. nigra with ants and ant food’ were applied. After one growing season, we tested differences in branching length and biomass of stems, roots and leaves. Certain genotypes showed significant differences in growth, but there were no significant differences in stem length, dry mass of stems and roots between the three treatments. The total biomass of poplars after the first growing season was positively affected by the initial size of the cuttings and was modulated by the genotype independently from the treatments. However, an increased poplar growth for the treatment without ants and with ant food was observed according to significant differences in dry weight of leaves and total biomass (i.e. dry mass of stems, roots and leaves) for the pooled genotypes across treatments. We discuss our results with the aim of serving as a reference for future in situ and ex situ experiments and field measurements exploring interactions between ants and poplars, specifically in riparian ecosystems.

Mound-forming ants are important ecosystem engineers as they increase habitat heterogeneity, thus supporting multiple biotic interactions. How these ant-mediated changes in abiotic factors translate into temporal biotic heterogeneity, is a less studied subject. In a case study localized on a Danish heath, we investigated how ant mounds (mineral and organic mounds) affected the phenology and flowering success of five plant species growing on or between ant mounds (Lasius flavus and Formica exsecta). Specifically, we focused on the phenophases’ stem elongation, flowering and seed set. All plant species showed significantly earlier phenophases on the mounds compared to control patches between mounds. These advances resulted in two distinct flowering seasons for one plant species and prolonged continuous flowering seasons for the four other species, when mound and non-mound plant seasons were combined. Likewise, stem elongation and seed set seasons were prolonged, with either two distinct seasons or one continuous season, depending on plant species. Two plant species exhibited increased survival up to the flowering stage when growing on ant mounds, since they flowered before a drought killed a large part of the population. Probable drivers behind these effects, as revealed by a structural equation model, were elevated surface temperature and other soil edaphic factors responsible for plant growth. Furthermore, the direct effects of the ant mounds were nearly twice as high for the organic mounds of F. exsecta compared with the mineral mounds of L. flavus. Possible implications are more resilient ecosystems, as prolonged seasons can mitigate phenological mismatches between interacting species.

Thrips (Thysanoptera: Thripidae) feed on leaf and flower tissue and some of them can be facultative predators. Caliothrips phaseoli Hood causes severe damage to different species of the Fabaceae family, mainly to Phaseolus vulgaris L. crops. The purpose of this research is to assess the change in feeding damage due to predation on Tetranychus merganser (Acari: Tetranychidae) eggs by the first and second larval stages of C. phaseoli on bean leaf discs, under laboratory conditions. Predation and damage were assessed through functional response and ordinal scale, respectively. The first and second larval stages of C. phaseoli exhibited a type II functional response. The second larval stage of C. phaseoli displayed shorter handling time and higher attack rate in comparison to the first instar. The first and second larval stages of C. phaseoli consumed 3.8 and 4.9 eggs of T. merganser per day, respectively. The second larval stage caused the highest damage (median = 3). The feeding damage of C. phaseoli was negatively associated to the number of eggs offered. The C. phaseoli larvae became more predatory than herbivorous when the number of eggs offered increased; therefore, C. phaseoli can be considered a facultative predator.

The behavioral phenotypes of hosts may be altered during parasitism, which could favor either the host or the parasite. Pea aphid Acyrthosiphon pisum hosts parasitized by the primary parasitoid wasp Aphidius ervi leave the stems or lower leaf surfaces where they are most commonly found and move to upper leaf surfaces before they die and mummify. In order to test whether the change of microhabitat benefits the host or the parasitoid, we transplanted pea aphid mummies reared in the laboratory to three different microhabitats on alfalfa plants in the field: the upper leaf surfaces, the lower leaf surfaces, and the stems. Survival analysis revealed no significant differences in mummy survival to emergence across the microhabitat treatments before an alfalfa harvest, when predation pressure was very high, and 2 weeks after an alfalfa harvest, when predation pressure was very low. In contrast, 5 weeks after an alfalfa harvest, when predation pressure was intermediate differences in predation risk were apparent: mummies transplanted to the upper leaf surface had the lowest mortality rates, mummies transplanted to the lower surface of leaves had intermediate mortality rates, and mummies transplanted to the stems had the highest mortality rates. Furthermore, a laboratory study suggested that, compared to other plant substrates, mummies on stems were more likely to be preyed upon by the ladybeetle, Hippodamia convergens, which concentrated its search on stems. Our results support the adaptive manipulation hypothesis, in that parasitized aphids appear to induce their host to move to a region of reduced predator foraging, where their risk of attack is reduced.

Mexico is the center of maize Zea mays L. domestication with a large diversity of landrace genotypes that are of great economic, cultural and social importance. Landrace maize genotypes are mainly cultivated by smallholder farmers for local and specialized markets of culinary dishes, However, all maize genotypes are subject to insect herbivory among which the Fall Armyworm (Spodoptera frugiperda Smith and the White grub larvae (Phyllophaga vetula Horn cause serious yield losses, by feeding on leaves and roots, respectively. Here we investigated the response of landrace and hybrid maize genotypes to herbivory from foliar (S. frugiperda) and root feeding (P. vetula) insects with five maize landrace and five hybrid maize genotypes. The main results showed that landrace maize genotypes suffered from a higher level of herbivory by S. frugiperda than hybrid maize genotypes. For root herbivory, no clear differences between landrace and hybrid maize were observed and overall, only one out of the five maize genotypes for each type of maize were negatively affected from the presence of P. vetula. In conclusion, maize genotypes respond differently to root and foliar herbivory, which should be considered when developing pest management strategies in maize agroecosystems.

Using knowledge about plant–insect interactions in a crop protection perspective is a pre-requisite to promote the development of novel pest management strategies. Enhancing plant natural defenses has been described as a promising way to improve the management of pests. In cotton, plant topping (cutting off the top of the plant) for inducing such defenses has been proposed as a promising tool for integrated pest management. The main objective of this study was to explore the effect of cotton topping on the performance of the cotton aphid, Aphis gosypii, under greenhouse conditions. The effect of plant topping was evaluated on topped and on neighbor non-topped plants. Results showed that cotton topping disturbed A. gossypii aphids not only on the topped plant but also on neighbor non-topped plants. The population of aphids grew slower in the topped compared to the control treatment and lower abundances of aphids were found in the topped treatment up to a distance of 100 cm to the topped plant. When an individual nymph was confined in a clip-cage, the production of winged adults after 15 days of confinement was higher in the topped compared to the control treatment. This difference decreased as the distance to the topped plant increased. In conclusion, our study proves that cotton topping mediates plant-pest interactions on the focal and neighbor plants. We discuss how cotton topping is a promising technique that could be used as part of an integrated pest management program, particularly for smallholders in West Africa, for controlling aphid infestations.

In Brazil, genetically modified cotton is increasing in most cultivated areas to manage insects, mainly Lepidoptera. Pests associated with cotton crops are diverse. Aphis gossypii Glover, 1877 (Hemiptera: Aphididae), one of the most important cotton pests, sucks photoassimilates from the phloem sap causing mold growth and damage to plant tissues. The interactions between Bt plants and non-target organisms and the impact of A. gossypii damage on these plants need further studies. Therefore, the objective was to evaluate the physiological stress caused by A. gossypii on Bt cotton and its isohybrid (same genetic background but not transgenic). The Bt cotton (Cotton Event 281-24-236/3006-210-23) and the isohybrid of this plant were planted in pots in a completely randomized design, as the treatments, with 30 replications in a greenhouse. The chlorophyll fluorescence parameters of the plants were evaluated by using a fluorometer. Regression models were adjusted for Bt cotton and the isohybrid, and the differences between treatments were evaluated through the model identity test. The photosynthetic parameters of Bt cotton and its isohybrid infested by this insect were similar.

Solanaceae is a large plant family whose center of diversity is in South America, it includes important crop plants and various weeds. Several species of Tephritid fruit flies have been reported in association with Solanaceous plants, particularly those in the genus Rhagoletis. However, many of these reports are on commercial crops such as tomato, and there is still little knowledge on use of wild native plants. Here, we report results of a 3-year survey of Solanaceous fruit in North-Western Argentina. Fruit of 22 species of Solanaceae were collected over 3 years in the Yungas, Dry Chaco, and Monte biomes. Fourteen of these plants were infested with dipteran, coleopteran, and lepidopteran larvae. Lycium sp. represents a new host plant record for Haywardina cuculi, Solanum aligerum is a new host plant record for Anastrepha fraterculus, Drosophila suzukii, and Rhagoletis blanchardi. Solanum argenteum, Solanum confusum, Solanum delitescens, Solanum pseudocapsicum, Solanum stukertii, and Solanum tenuispinum are new host plant records for Rhagoletis blanchardi. Solanum trichoneuron is a new host plant record for Anastrepha fraterculus. Two unidentified species of Lonchaeidae were found infesting nine species of Solanaceae. Hymenopteran parasitoids in the genus Utetes, Doryctobracon, and Ganaspis were found in association with Solanaceae infesting tephritids. We also report notes on the life cycle and behavior of the tephritids recovered during this sampling effort.

Plants are frequently exposed to heat stress as a result of global warming. Heat stress leads to a series of physiological responses including stress volatile elicitation, but how heat stress-induced volatile cues affect the behavior of herbivores is poorly understood. In this study, the polyphagous herbivore Spodoptera litura (tobacco cutworm, TCW) and Chrysanthemum nankingense were selected as the model to elucidate the interactions between herbivore behavior and heat stress-induced plant physiological changes. Photosynthetic characteristics and volatile emissions were measured in C. nankingense control plants (25 °C for 3 h), in C. nankingense exposed to moderate (35 °C for 3 h), and severe (45 °C for 3 h) heat stresses. Net photosynthetic rate (An) decreased by more than two-fold after exposure to 45 °C due to non-stomatal inhibition of photosynthesis. 45 °C treatment induced emissions of the camphor and (E)-β-caryophyllene. Exposure to 35 °C had minor effects on photosynthetic characteristics and did not induce terpene emissions. Using dual-choice olfactometer bioassays, we found that 45 °C treatment enhanced the attractiveness of the plants to TCW. Moreover, the leaf concentrations of nine sesquiterpenes were increased and the feeding of TCW was strongly inhibited after 45 °C treatment compared with control plants. Taken together, our study highlights the impact of heat stress on the behavior of the herbivore mediated by the accumulation and emission of sesquiterpenes and suggests altered pest-host interactions under future warmer climates. Modulation of terpenoid emissions and contents should be considered in developing future ecological pest control strategies in agricultural fields.

Previous laboratory studies have shown that diesel exhaust can differentially degrade the volatile organic compounds (VOCs) that constitute floral odors. Furthermore, in proboscis extension response studies honey bees have been shown to have reduced recognition to these degraded floral odors. In this study, we investigated whether flower odors exposed to diesel exhaust reduce foraging in free-flying bees and if flower color influences bees’ behavior. Therefore, we conducted a field study in which honey bees were trained to visit the locations of two arrays of artificial flowers. From the artificial flowers, honey bees were presented with floral VOCs combined with either fresh air or diesel exhaust, through different colored flowers (black, blue, red, and yellow). Honey bee visitation rate did not differ between volatiles delivered with fresh air or with diesel exhaust, suggesting that revisitation of previously rewarding flower patches may be unaffected by air pollution. We also observed a significant interaction between treatment and color: blue flowers were more attractive when volatiles were delivered with diesel exhaust, which was the other way around for red and black and played no role in yellow flowers. Generally, honey bee foraging behavior seemed to be influenced by their previous experiences.

Nectar dynamics and nectar sugar composition play an important role in attracting floral visitors. Though butterflies are considered next to honeybees as pollinators, their contribution to pollination remains under explored. The present study is a first report of the nectar production, standing nectar crop, nectar sugar composition and butterfly visitors of Leucas stelligera, a genus endemic to Western Peninsular India and Ixora coccinea, native to the tropics and sub tropics. Nectar volume of bagged (24 h- production) and unbagged (standing crop) flowers at different hours of the day was determined. Floral nectar was analyzed for sugar composition using High-Performance Liquid Chromatography. Butterfly floral visitors were observed for the two plant species. L. stelligera and I. coccinea produced 3–26 µl and 2–13 µl of nectar in bagged flowers with highest volume at 09.00 h and 12.00 h, respectively. There was increase in the coefficient of variation in nectar production for both the plant species after 15.00 h. Sucrose-dominant nectar was observed in L. stelligera and glucose-dominant in I. coccinea. Butterfly visitors of L. stelligera included species belonging to family Papillionidae, Nymphalidae, and Lycaenidae along with hymenopterans. Butterfly species belonging to family Papilionidae, Nymphalidae, Pieridae, and Lycaenidae were recorded on I. coccinea. Both the species had marked temporal fluctuations in nectar production volumes and standing nectar crop.

Wildflower strips are increasingly promoted in pollinator conservation schemes to maintain the stability of ecosystem services and increase crop yield. Yet, the increased area of avocado Persea americana Mill. cultivation in sub-Saharan Africa is not accompanied by measures of biodiversity conservation or the promotion of ecosystem services. We investigated the effects of flower strips on flower visitors and avocado fruit set in Kenya. A strip mixture of sunflower Helianthus annuus L., coriander Coriandrum sativum L., and alfalfa Medicago sativa L. was established at the border of four avocado plots, while four other plots with an unmanaged border served as control. The abundance of insect flower visitors and fruit set at 10 m, 55 m, and 100 m from the border of each plot were assessed during the early, peak, and late avocado flowering periods. The honeybee Apis mellifera L. and hoverflies Syrphidae spp. accounted for 22% and 71% of flower visitors, respectively. We found interactions between the treatment, distance to the border, and the avocado flowering intensity on the abundance of honeybees but not on hoverflies. Irrespective of the distance to the border and the avocado’s flowering intensity, flower strips acted as a sink for honeybees and hoverflies. Overall, the flower strip mixture of sunflower, coriander, and alfalfa did not increase pollinator abundance and avocado productivity, and it may be necessary to identify plant species for optimal benefits and study the long-term effects of floral strips on pollinators and crop production.

A potential alternative to the use of chemicals for controlling phytophagous arthropods in agricultural environments is the use of biological control agents of natural occurrence. This study evaluated the functional response of first-instar larvae of Chrysoperla externa-fed eggs and nymphs of Aleurodicus cocois, as well as the olfactory response of the third-instar larvae of this predator to the volatiles of two genotypes (CCP 76 and PRO 143/7) of dwarf cashew induced by the herbivory of A. cocois. The volatile compounds emitted by the leaves of the two cashew genotypes, infested and non-infested by A. cocois, were analyzed by solid-phase microextraction coupled to GC–MS. Logistic regression indicated that first-instar larvae of C. externa exhibited a type II response when fed eggs and nymphs of A. cocois. The value of the attack rate (a') did not differ between prey, but the handling time (Th) was longer when the predator fed on nymphs. In the behavioral tests third-instar larvae of C. externa were able to distinguish and select the volatile signals emitted after the infestation of A. cocois, regardless of the cashew genotype evaluated. According to the volatile profiles of cashew genotypes infested by A. cocois, the compounds β-caryophyllene, allo-ocimene, neo-allo-ocimene, α-copaene, γ-muurolene, and δ-cadinene were released in large amounts by genotypes CCP 76 and PRO 143/7. Therefore, these compounds may be involved in the attractiveness of the predator. The results indicate that C. externa may be an effective biocontrol agent of A. cocois in cashew crop.

One of the most peculiar biological interactions between pollinators and plants is the use of flowers as sleeping places, but this phenomenon is still poorly understood and it has been proposed to use citizen science in the form of volunteer records to fill the knowledge gaps. In this work, we report for the first time on the use of flowers as sleeping places by five species of Chilean flies of the genus Lasia (Acroceridae) in central Chile. In addition, we seek to determine whether the flower shape and/or color might be good predictors for flies using them as sleeping places. We used standardized records from a long-term citizen science project that exclusively monitors flies. We counted the number of flies that used flowers as a sleeping place and discretized the morphological variables of the flowers to relate both responses and predictors with a generalized linear model. We found that flowers belonging to the genus Alstroemeria, followed by Clarkia and Salpiglossis, were the most used as sleeping places. Our results suggest that zygomorphic flowers (with bilateral symmetry, and usually tubular flowers) are a better predictor than actinomorphic flowers and their color. The use of zygomorphic flowers could represent a better option for flies in adverse environmental conditions or to avoid predators, but the use of flowers as sleeping places could be an as-yet poorly understood way of pollinating plants. Citizen science, although it has some limitations (taxonomic, spatial or temporal biases), has great potential for describing new biological interactions in a changing world.

Field margins have an important ecological role in agroecosystems including hosting beneficial insect such as syrphids. However, little is known of syrphid preferences for different types of field margins. Syrphids were sampled in field margins in an organic agroecosystem to test the hypothesis that syrphid abundance in field margins depends not only on the floral resource abundance but also on field margin component type, field margin complexity, and adjacent land-use type. Floral resource abundance had the greatest influence on the number of syrphids surveyed. Field margin characteristics were deemed to effect syrphid abundance both independently of their effect on floral resources and by altering floral resource abundance. Syrphids were more abundant in field margins adjacent to cropped fields than those adjacent to grazed fields or roads. More syrphids were found in ditch components than in tree or grass strip components. The influence of floral resources on syrphid abundance varied depending on their botanical families, although no significant differences were observed for the effect of botanical family floral resource index on syrphid abundance. These findings demonstrate that field margin characteristics play an important role in facilitating plant–syrphid interactions and offer an insight in agroecosystem management for the promotion of beneficial insects. The influence of field margin characteristics on other beneficial insect groups should also be investigated.

Spodoptera frugiperda (fall armyworm; FAW) is a generalist herbivore that has a severe impact on crop production. Due to its wide range of host plants, FAW fitness on weeds was evaluated. Field dodder (Cuscuta campestris Yunck.) is an obligate parasitic plant that severely impacts crop production, and the disposal of C. campestris residue needs to be handled carefully. Therefore, finding an alternative application may be the best method for disposal. In this study, extracts from fresh C. campestris tissues, dried tissues, and seeds were tested for their antiherbivore effect on FAW. The ethanol-based extracts from fresh and dried C. campestris tissues exhibited a lower FAW larval survival rate than the control, while treatment with the ethanol-based C. campestris seed extract had no effect. The extract was heated to characterize the inhibitory substances. The heat treatment did not affect the detrimental impact of the C. campestris extract on the FAW survival rate. In addition, the ethanol-based C. campestris extract had a lower FAW larval survival rate than nonparasitized wedelia [Sphagneticola trilobata (L.) Pruski], the host plant of C. campestris. However, parasitized wedelia extract had a similar effect on the FAW survival rate as the C. campestris extract and nonparasitized wedelia extract. This study reveals that C. campestris extract has potential applications as a botanical-based pesticide to control FAW.

Plant–herbivore relationships involve a significant amount of global biodiversity within complex interaction networks. Buprestidae (Coleoptera) are highly specialized herbivores, and several species have important economic and ecological impacts. We used tools derived from network theory to evaluate the structure of a plant-buprestid metaweb at three different organizational levels (network, subnetwork, and species-levels) and test whether trophic guilds and taxa differ in their patterns within the network. We also tested whether taxonomically closely related buprestid species are more likely to share the same host plant species. We found that the plant-buprestid metaweb exhibits a non-nested and significantly highly modular pattern, and most buprestid and host plant species have specialized interactions. Florivorous buprestids showed the highest diversity of host preferences and, together with Fabaceae, were the most important for the network structure as they are highly connected species. Leaf-mining buprestids had the most extreme interaction pattern among trophic guilds, with high modularity and specialized interactions. We also found a low probability to share the same group of host plants among buprestids, which decreased with taxonomic distance. Our findings uncover patterns within a plant–herbivore network at large spatial scales and at different taxonomic levels, which are shaped by the diversity of host and resources preferences, more than taxonomic relatedness. Those network patterns might reflect different ecological roles for each trophic guild and taxa. We highlight the relevance of considering the diversity of feeding habits within networks of a single type of interaction and emphasize the importance of analyze network patterns at high levels of organization.

Diceraeus melacanthus Dallas, (Hemiptera: Pentatomidae) is a polyphagous stink bug that has been reported to be an important pest in maize and soybean. Control of this herbivore in crops is achieved using insecticides. Use of companion plants to control and manage herbivores in crop areas has been proposed, but there are still few systems that have been deployed to growers. Trap crops work by attracting herbivores, removing them from target plants, or/and attracting their natural enemies. Observations in our laboratory revealed that female D. melacanthus oviposit in Cajanus cajan L. Millsp (Fabaceae) pods. Therefore, the aim of this study was to evaluate whether C. cajan plants have potential for use as trap crops for D. melacanthus. In the current study, we evaluated the oviposition behaviour of D. melacanthus and its preference for different substrates, such as cotton bolls, C. cajan, Glycine max L. Merril (Fabaceae) and Phaseolus vulgaris L. (Fabaceae) pods; their behavioural response to constitutive volatiles emitted by C. cajan plants at different phenological stages; and the effect of non-volatile compounds of C. cajan pod on oviposition preference. The results revealed that D. melacanthus females prefer to oviposit on C. cajan pods, cotton bolls rubbed on C. cajan pods or cotton bolls treated with quercetin over cotton bolls and P. vulgaris pods. D. melacanthus females recognize and are attracted by volatiles of reproductive C. cajan plants. In addition to the preference for ovipositing, the offspring of D. melacanthus does not survive on C. cajan pods. Our results suggest that C. cajan plants have the potential to be evaluated as a trap crop for D. melacanthus.

Phenotypic variation in plants induced by biotic stressors can have cascading effects throughout arthropod communities. Habitat modifiers increase habitat complexity, which may promote species diversity and change arthropod species composition. A taxonomic approach to describe arthropod communities together with a trait-based approach might reveal mechanisms behind taxonomic changes and consequences for ecological processes. We previously found that the mistletoe Tristerix aphyllus induces susceptibility in the cactus Echinopsis chiloensis to the stem-borer beetle Xyletomerus sp., a habitat-modifier that drills brood chambers on cactus. Further, the community of arthropods that colonized chambers on parasitized cacti was more diverse and was different in composition compared to that found in chambers of non-parasitized cacti. We do not know whether the effects of brood chambers extend to the whole mistletoe-cactus system and how the arthropod community responds to seasonal phenology of mistletoe. Here we experimentally reduced the number of brood chambers and examined the effects on taxonomic and functional richness and composition, considering mistletoe seasonal phenology. We found a positive relationship between the number of chambers and arthropod species richness, abundance and functional richness. Arthropod taxonomic and functional richness were generally higher at mistletoe flowering compared to fruiting or mistletoe senescence/cactus flowering stages. Species composition varied with chamber number and changed with mistletoe seasonal phenology. Functional composition changed with mistletoe phenology. Functional richness and species richness were positively correlated, yet, functional redundancy is likely to occur. We conclude that cascading effects initiated by mistletoe extends beyond the chamber scale, up to the plant scale.

It is well established that host plants influence an insect's immune responses; however, most studies have been conducted on lepidopteran insects; little is known about hemipteran insects, particularly the pea aphid, Acyrthosiphon pisum. Pea aphids feed on host plants by ingesting phloem sap. The chemical composition and concentration of the sap vary depending on the host plant. These differences may impact aphid immune responses to pathogens. In this study, we examined the variations of the immune responses of pea aphids reared on broad beans (Vicia faba) and alfalfa (Medicago sativa). Pea aphids on these two host plants were challenged with bacteria Staphylococcus aureus and Escherichia coli and then the concentration of hydrogen peroxide (H 2 O 2), phenoloxidase (PO) activity, and phagocytosis index were measured. We found that the H 2 O 2 level and PO activity increased in the aphids on these two host plants in response to bacterial infection. In the infected condition, aphids reared on broad beans had higher H 2 O 2 level than those reared on alfalfa, on the contrary, aphids reared on alfalfa had higher PO activity than those reared on broad beans. Furthermore, for both groups of aphids, haemocytes engulfed bacterial cells, and the capacity to phagocytize did not vary significantly between the haemocytes from these two groups of aphids. Our findings suggested that the immune responses of the pea aphid to pathogen are affected by their host plant specifically.

Diabrotica speciosa (Germar) is a pest of economic importance for several crops in South and Central America, causing damage to plants in both the larval and adult stages. This study aimed to develop methodologies for evaluating the oviposition preference of D. speciosa for maize genotypes. Plants were grown in a greenhouse and brought to the laboratory to perform the experiments. We evaluated (i) the ability of D. speciosa to recognize the most suitable maize oviposition host; (ii) the optimal number of D. speciosa pairs per maize plant; (iii) the preferred plant age for oviposition; (iv) the effect of adult feeding resource on oviposition and survival; and (v) the oviposition preference of D. speciosa on maize genotypes selected from previous studies. D. speciosa females were able to identify the presence of a maize plant for oviposition, compared to a substrate without a plant. However, females were unable to discern the best host plant for the development and survival of their offspring when different maize genotypes were assessed. The presence of bean plants (Phaseolus vulgaris L.) as an additional food source increased the number of eggs laid by D. speciosa. Conversely, the absence of bean plants resulted in higher adult mortality in the experiments. Additionally, this study showed that maize genotypes with antibiosis characteristics do not always manifest in repellence or deterrence of oviposition. There may be no correlation between antibiosis and oviposition preference in the interaction between D. speciosa and maize plants.

The predatory mite Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae) is a commercially available natural enemy of phytophagous mites and insects. The current study tested the utility of plant pollen as a non-prey diet for mass rearing A. swirskii was tested in this study. Experiments tested the effects of almond Prunus amygdalus Batsch pollen on biological parameters and population growth of A. swirskii from the 1st to the 45th generation (G1–G45) and predation of Tetranychus urticae Koch (Acari: Tetranychidae) before the 1st generation (B-G1) and after the 45th generation (A-G45). Results indicated that the intrinsic rate of increase (r) and finite rate of increase (λ) were lowest in G1 and G3 and both increased and reached their highest values in G20, then decreased slightly and remained constant from G25 to G45. Comparison of the performance of A. swirskii between B-G1 and A-G45 indicated that pre-imaginal duration time was significantly longer for B-G1 than for A-G45. Total pre-oviposition period and oviposition days were significantly longer for B-G1 than for A-G45. Adult longevity was greater for A-G45 than B-G1. Furthermore, life table parameters R0, r, and λ were significantly higher for A-G45 than for B-G1. Finally, net predation rate (C0), transformation rate (Qp), and finite predation rate (ω) were significantly higher for A-G45 than for B-G1. Overall, the results of this study suggest that almond pollen is suitable for long-term rearing of A. swirskii. Almond pollen may enhance A. swirskii predation capacity but further experiments on infested whole plants are necessary to confirm the results reported herein.

Oak hybridization have important effects on the structure of herbivorous insect communities and associated natural enemies. We tested the effects of hybridization between Q. magnoliifolia and Q. resinosa on insect gallers trophic networks and their parasitoids. We characterized the genotypes of 35 individuals of Q. magnoliifolia, 30 of Q. resinosa, and 57 hybrids using eight nuclear microsatellite markers. We collected 6,798 galls from the oak hybrid complex distributed in 33 gall morphospecies on Q. magnoliifolia, 28 on Q. resinosa, and 42 on hybrid oaks. Galler-parasitoid networks were realized by 21 gall morphospecies and 21 parasitoid species for Q. magnoliifolia; 16 gall morphospecies and 30 parasitoid species for Q. resinosa; and 25 gall morphospecies and 23 parasitoid species for hybrids. Plant-galler networks were different among three oak groups, having the hybrid network higher values of diversity of interactions, nestedness and modularity and lower values of specialization than Q. magnoliifolia and Q. resinosa networks. Hybrid network of gallers and parasitoids had higher diversity of interactions, connectance and generality and lower modularity than Q. magnoliifolia and Q. resinosa networks. Hybrids are more vulnerable to insect galler incidence having low pressure by parasitoids, which allow more gall incidence in hybrid plants. Our study corroborated that hybridization generates changes in oak genetic composition influencing insect gallers trophic networks and their parasitoids. Our findings are also consistent with the rule of genetic similarity which suggest a relationship between plant genetics and the associated arthropod community, where genetically similar plants support similar arthropod communities.

Plants employ defense strategies to reduce or prevent attacks by phytophagous insects and survive. These strategies can involve chemical constituents that are synthesized to be toxic or repellent to arthropods. The tomato leaf miner, Tuta absoluta, damages tomatoes on all continents. This insect can reduce yield and increase control costs. Genetic breeding can help improve the management of this pest. Therefore, the present study studied the resistance and toxicity of the main chemical constituents of tomato plants to T. absoluta. Bioassays of antixenosis, antibiosis and relative toxicity of chemical constituents were performed. T. absoluta were subjected to concentration–mortality bioassays using 2-tridecanone, p-cymene, α-tomatine and coumarin. Heterosis was examined in three hybrids for resistance to T. absoluta that could be used in plant breeding programs. The 2-tridecanone constituent was the most toxic chemical that most reduced leaf consumption by T. absoluta larvae. Our results showed that these chemical constituents (e.g., 2-tridecanone) could be used as a target for tomato breeding programs and perhaps sprayed to repel insects or applied as a contact insecticide.

Many plants have red/purple young leaves, and it has been proposed that the red/purple colouration reduces herbivory. Possible mechanisms underlying herbivory avoidance by red/purple young leaves were investigated using a generalist grasshopper Atractomorpha lata. To determine whether red/purple leaves reduce herbivory by the grasshopper, choice tests between purple and green perilla leaves were conducted under three light conditions, namely, exposure to white light, blue light, and darkness. Only under white light, A. lata ate more green leaves than purple leaves. Therefore, purple colouration of leaves is effective in preventing herbivory by A. lata. Young leaves of Annou-imo, a variety of sweet potato, are reddish brown or purple, and the colour changes to green when the leaves mature. The purple leaves contain a higher concentration of phenolics and latex than do the green leaves, and A. lata nymphs fed on the purple young leaves of Annou-imo exhibited worse growth than those fed the green mature leaves. Therefore, the red/purple colouration of young leaves is likely a warning signal to herbivores. When green herbivorous insects are positioned on red/purple leaves, they are conspicuous to enemies. Herbivores may have evolved to actively avoid red/purple leaves to maintain colour matching between their body and the background. I investigated whether A. lata exhibited a colour preference for substrates other than leaves, but they did not select a background that matched their body colour.

Olfaction and chemical ecology in phytophagous ladybird beetles have been largely ignored so far. The present paper describes for the first time basiconic, grooved, and trichoid porous olfactory sensilla on the antennae of the phytophagous ladybird Chnootriba elaterii (Epilacnini) and demonstrates the sensitivity of the antennae to Volatile Organic Compounds (VOCs) from host plants, belonging to common and less common Cucurbitaceae crops and wild species (Citrullus lanatus, Cucumis melo, Cucumis sativus, Cucurbita pepo, Cucurbita moschata, Lagenaria siceraria, Luffa cylindrica, and Ecballium elaterium). Epilachnini ladybirds are phytophagous, with adult and larvae feeding on various Cucurbitaceae, Fabaceae, and Solanaceae. Notwithstanding some species are serious pests in crops, their chemical ecology has been largely disregarded so far. The present paper discusses the ultrastructure of antennal sensilla (scanning electron microscopy-SEM) and the electroantennographic recordings (EAG) from the olfactory sensilla responding to the proposed chemicals, also considering the literature on chemical ecology and olfaction of aphidophagous ladybugs. In particular, antennal sensilla are similar to those described in predatory species but in Epilachnini they are much more numerous on the apical flagellum, probably because involved in host plant location and selection. This research can be considered a first step in developing semiochemical-based and sustainable control strategies for melon ladybird in crops.

Bipartite networks of flowering plants and their visitors (potential pollinators) are increasingly being used in studies of the structure and function of these ecological interactions. Whilst they hold much promise in understanding the ecology of plant–pollinator networks and how this may be altered by environmental perturbations, like land-use change and invasive species, there is no consensus about the scale at which such networks should be constructed and analysed. Ecologists, however, have emphasised that many processes are scale dependent. Here, we compare network- and species-level properties of ecological networks analysed at the level of a site, pooling across sites within a given habitat for each month of surveys, and pooling across all sites and months to create a single network per habitat type. We additionally considered how these three scales of resolution influenced conclusions regarding differences between networks according to two contrasting habitat types (urban bushland remnants and residential gardens) and the influence of honey bee abundance on network properties. We found that most network properties varied markedly depending on the scale of analysis, as did the significance, or lack thereof, of habitat type and honey bee abundance on network properties. We caution against pooling across sites and months as this can create unrealistic links, invalidating conclusions on network structure. In conclusion, consideration of scale of analysis is also important when conducting and interpreting plant–pollinator networks.

Trophic cascades among plants, herbivores, and natural enemies can be affected by agriculture planting shifts from complex (polyculture) to simple (intensive). Yet, the information on regulation of trophic relations in organic agriculture is limited. To address this, we explore the impacts of plant species richness on composition of three functional groups of arthropods (pest, natural enemies, and neutral insects), as well as the richness and temporal stability of natural enemies. We tested four plant species richness levels and divided into 24 similar sized small field plots on an organic farm. We found 48 species of arthropods (29 species of pests, 9 species of predators, 4 species of parasitoids, and 6 species of neutral insects), with their abundance and species richness significantly increased with increasing plant species richness, suggesting a bottom-up effect. Total arthropod stability (pests, natural enemies, and neutral insects) increased with plant diversity, but individual species stability decreased for most arthropods, which resulted from enhanced structural diversity and reduced resource specificity in these plots. Plant species richness was significantly correlated with specialist and generalist pest and natural enemy species abundance as well as their stability. These findings suggest diverse organic farming to better sustain generalist predators with increased provision of food resources and breeding habitats.

Amendment of soil with Silicon (Si) is known to enhance plant resistance against insect pests and can be used as a tool to improve management of rice stem borers on rice. A study was conducted to investigate the use of Si to induce resistance in rice plants and the effects of Si on the development of Diatraea saccharalis (Lepidoptera: Crambidae). The experiment was carried out in a 3 × 3 factorial scheme (cultivar × Si) arranged in a randomized complete block with four replications, where the rice cultivars Canela de Ferro, BRS Esmeralda and IR 42 were combined with a mixture of calcium and magnesium silicate at three rates (control, 300 and 600 kg ha −1) applied in the soil before seeding. Plants were infested with 10 neonate larvae/pot at pre-flowering stage (60 days after plant emergence). Twenty-five days after infestation, plants were cut at ground level and taken to the laboratory where the stems were examined and the following variables determined: silicon content, number of live larvae, larval weight, relative growth rate of larvae, number of total stems (tillers), number and percentage of damaged stems and larval boring success. Si caused a negative effect on D. saccharalis development on Si treated plants compared to non-treated plants. Si treated plants were less damaged compared to non-treated plants. Amendment of soil with Si proved to be effective to enhancing rice resistance to rice stem borer, probably due to the increase of Si content in plant tissues. The response of susceptible rice cultivar to Si application indicates that adding silicates to soil is a good tool for reducing infestation and damage of stem borers to rice.

Eucera and Xenoglosa are the two most frequent squash pollinators, and they both rely solely upon plants of the genus Cucurbita for pollen intake to feed their offspring. The present study reports the first case of Eucera fervens individuals infected with Nosema ceranae spores and assesses the possible impact of this microsporidian on the squash pollen transportation carried by this South American native bee. From the total 963 bees visiting pumpkin flowers, the most frequent bee species was E. fervens (89.8%). A total of 90 bees were sampled for pollen count and Nosema detection. Bees were carrying an average of 62 pollen grains (7–426) and an average of 19 Cucurbita pollen grains (1–93). Nosema was present in 98% of the samples (71/72), while its mean intensity was 1.65 × 10⁶ spores (1.5 × 10⁵–6.78 × 10⁶). A positive correlation between the total pollen grains and the number of pumpkin pollen grains transported by E. fervens was observed. The Cucurbita maxima pollen transported by E. fervens was not explained by N. ceranae spores loads. Nevertheless, a positive correlation between the total pollen grains transported by E. fervens and the N. ceranae intensity was observed suggesting and effect of the microsporidian on bee behavior.

Biological invasions are regarded as a major threat to native biodiversity, with cascading ecological and economic consequences within invaded areas. Anticipating and managing these invasions requires a better understanding of the interactions between non-native and native species. We compiled a list of alien plant species and their native insect herbivores from various terrestrial habitats in the Kashmir Himalaya. On alien plants, a total of 15 native insect herbivores were found, four of which were specialists (Aglais caschmirensis on Urtica dioica, Agrotis sp. and Chrysolina herbacea on Mentha longifolia and Nezara viridula on Verbascum thapsus) and the rest were generalists. Altica himensis is the most common native insect herbivore, feeding on nearly 31 alien plants. Various diversity indices show a quantitative estimate of the alien plant and native insect herbivore network. A total of 42 alien plants were recorded throughout the course of 2 years (2018–2020), with Plantago major having the highest relative abundance of 9.7. The study provides a baseline information on the challenging issue of biological invasion by highlighting the role of native insect herbivores as natural biocontrol agents against invasive alien plants.

An early arrival of natural enemies on infested plants while pest density is still incipient is ideal to attain successful biological control. The recruitment of distant natural enemies to a newly infested area is likely to entail primarily the use of long-distance visual cues from plants. Therefore, studying the role of long-distance cues in the attraction of natural enemies to a given habitat is paramount to devise proper recruitment-strategies. Nevertheless, not all natural enemies respond the same way to long-distance cues as their movement behavior varies across species. In this field study, we investigated whether the visual cues from insectary plants (alyssum flowers) could favor an early arrival of distant natural enemies on aphid-infested brassicas located nearby the flowers. Furthermore, we examined if different guilds of natural enemies (epigeal vs. flying ones) would have different responses to the visual cues. The experiment followed a split-plot design consisting of two whole plots (presence vs. absence of flowers) and three subplots i.e. aphid access to (i) epigeal, (ii) flying, and (iii) both natural enemy types. Our results suggest that visual cues from alyssum flowers promoted a faster recruitment of parasitoids. Nevertheless, our findings suggest that predators may not rely on visual cues from the insectary plants, but instead use mostly visual cues from the host plants to make their first approach. Lastly, the results show that the movement behavior was key in the early recruitment of natural enemies, suggesting that flying natural enemies may be able to use distant visual cues more efficiently.

The role of leaf cuticular wax of cabbage, Brassica oleracea L., rapeseed, B. campestris L., and Indian mustard, B. juncea L. in host preference by two generalists, Spilarctia obliqua Walker and Pieris brassicae L., and a specialist, Plutella xylostella L. was investigated under laboratory conditions. A total of 25 n-alkanes from n-C14 to n-C36 and 15 free fatty acids (FFAs) from C12:0 to C22:0 were detected from leaf cuticular wax of three crops with significant variations in their respective quantities (µg leaf⁻¹). The most preferred wax chemicals were consisted of 5 n-alkanes (n-C16, n-C18, n-C20, n-C22, n-C30) and 5 FFAs (C12:0, C16:0, C18:3, C18:2, C18:1) for the pests. Highest attraction index (AI%) and oviposition preference index (OPI%) were in the order of P. brassicae > P. xylostella > S. obliqua and P. xylostella > P. brassicae > S. obliqua, respectively, toward the combined synthetic mixture (5 n-alkanes + 5 FFAs) treated leaf of cabbage due to higher amount of wax chemicals in the specific combination. Both generalist and specialist have same patterns of olfaction and oviposition preferences with different magnitude of responses. Thus, the synthetic blends of same 5 n-alkanes and 5 FFAs of the most preferred cabbage cultivar might be used as lure to develop baited trap as well as less preferred crop (rapeseed and Indian mustard) species might be used as main crop with cabbage as trap crop against the pests for their sustainable ecological management in near future.

Cowpea aphid (Aphis craccivora Koch.) is an important pest of cowpea. This study aimed to identify aphid resistant cowpea (Vigna unguiculate (L.) Walp.) genotypes derived from three susceptible varieties widely grown in Zambia (Bubebe; Lutembwe and Msandile) after mutagenesis by gamma radiation. Eleven genotypes derived in this way were evaluated: six (BB3, BB7, BB8, BB10, BB14 and BBV) from Bubebe, three (LT3, LT4 and LT11) from Lutembwe and two (MS1 and MS10) from Msandile. Aphid resistance was evaluated by recording aphid colony growth, mean relative growth rate (MRGR), intrinsic rate of natural increase (rm), doubling time (DT) and feeding behaviour when reared on each genotype. Where colony growth was recorded, significantly lower numbers of aphids were recorded on genotypes BB7, LT3, LT4 and LT11 compared to their parents (Bubebe and Lutembwe). Genotypes LT3, LT4 and LT11 also resulted in lower aphid MRGRs, rm and DT compared to the parent. Slower colony growth, MRGRs, rm and DT on genotypes LT3, LT4 and LT11 and slower colony growth only on genotype BB7 suggests the presence of mutation derived resistance to cowpea aphid. Characterisation of feeding behaviour on LT3, LT4 and LT11 using electrical penetration graph recording showed that resistance to cowpea aphid is mediated by epidermal and mesophyll-based resistance factors. BB7, LT3, LT4 and LT11 are therefore promising genotypes that should be evaluated further for genetic improvement of cowpea against the cowpea aphid. This study highlights the potential contribution of induced mutagenesis in the integrated management of aphid pests.

The defense mechanisms that plants have developed in response to herbivory can be chemical, physical, or morphological, which, acting alone or combined, can reduce the damage caused by insects. In this study, the morphogenetic traits capable of attributing resistance to common bean cultivars to Diabrotica speciosa were analyzed, which will serve as a basis for use in the organic system and serving as parents to compose variability in breeding programs. The susceptibility and resistance of cultivars to D. speciosa were determined through tests of feed preference no-choice and free-choice and preference for consumption, the enzymatic activity of CAT, POD, and SOD, expression of PvbZIP1, PvWHIRLY3 and PvNPR1 genes, analysis of morphological and chemical components of the plant. The studied morphogenetic components showed insect-plant interaction, where the cultivars, in response to damage caused by D. speciosa increased enzyme activity and expression of defense genes. Trichomes in the abaxial surfaces of the leaves, and phosphorus content demonstrated a negative correlation with the feed preference and consumption by D. speciosa. The resistance of the cultivars to D. speciosa was also correlated with nitrogen, sugar, and chlorophyll content since they can modify the plant’s chemical composition and increase resistance to herbivory. Morphogenetic analysis indicates that BRS Esplendor and IPR Curió has traits providing greater susceptibility, while IPR Uirapuru and IPR Tangará present features bringing greater resistance to D. speciosa. Therefore, they are promising genotypes for cultivation in an organic system and as parents to compose variability for breeding programs, research development, and selection to resist D. speciosa or other herbivorous insects.

Climate change (rise in temperature, CO2 level, etc.) poses a serious threat to the agriculture sector. Therefore, it is necessary to develop and adopt new methods to cope with climate change. The army worm, Spodoptera litura (Lepidoptera: Noctuidae) is a destructive pest of many crops including castor bean in tropical regions of the world. The insect’s development, reproduction, food uptake, and body size on castor bean was assessed at five constant temperatures (15, 20, 25, 30, and 35 °C). Green Lacewing, Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae) is an important general predator. The predation rate dependency on temperature is also a concern in scenarios of climate change. Therefore, we studied predation by C. carnea at similar constant temperatures on eggs (with hairs and without hairs) and first instar larvae of S. litura. Immature stages of S. litura complete their duration at 15 to 35 °C. Optimum survival of all immature stages ranged from 25 to 27 °C according to polynomial survival model. There was no egg laying by S. litura at 15, 30, and 35 °C but a maximum of eggs (5212 eggs/female) were laid at 25 °C. The larval instar’s length did not follow temperature size rule, but pupal weight did. Only third and fourth instars of S. litura significantly increased their diet consumption at the warmest temperature (35 °C). The lower developmental threshold of all immature stages ranges from 10 to 11 °C, calculated by linear model. Non-linear mathematical models were used to calculate the upper developmental thresholds for larvae, pre-pupae, and pupae ranges which range from 39.3 to 43.0 °C. The predation rate of C. carnea increased with the increase in temperature from 15 to 35 °C, and more eggs without hairs, and first instar larvae of S. litura, were consumed than eggs with hairs. The suitability of castor bean as a host for mass rearing of S. litura is evident from our results at 25 °C. The study demonstrates the potential use of C. carnea to control S. litura on castor bean. We also discuss our results in context of the potential of castor bean as a trap crop for S. litura.

Bemisia tabaci (Gennadius, 1889) (Hemiptera: Aleyrodidae) is one of the main phytosanitary problems found in tomato crops (Solanum lycopersicum L.) in Brazil, causing direct and indirect damage and consequently, physiological and biochemical damage to host plants. This study’s objective was to evaluate the influence of B. tabaci MED and MEAM1 infestation on the physiological and biochemical properties of tomato during the flowering stage. Plants infested with B. tabaci MED and MEAM1 and non-infested plants (control) were studied. Gas exchange, chlorophyll fluorescence, and biochemical parameters (superoxide dismutase (SOD), peroxidase (POD), polyphenol oxidase (PPO), and total phenols) were analyzed. Stomatal conductance (Gs), internal CO2 concentration in leaves (Ci), and transpiration (E) in B. tabaci MED-infested tomato plants were 45 and 38%, 10 and 33%, and 42 and 33% lower than in the control and B. tabaci MEAM1-infested plants, respectively. However, the water use efficiency (WUE) in B. tabaci MED- and MEAM1-infested plants was 38 and 12% higher than in control plants. Plants infested with B. tabaci MEAM1 showed reduced POD activity in the development stages, 3rd and 4th instars, when compared to plants infested with B. tabaci MED by 41 and 50%, respectively. B. tabaci MED-infested plants had lower enzymatic activity (SOD, POD, and PPO) and total phenols at oviposition compared with B. tabaci MEAM1-infested plants. B. tabaci MED infestation during the flowering stage caused alterations in the physiological parameters of tomato plants, while B. tabaci MEAM1 infestation showed less activity of the POD enzyme at all insect pest development stages. Graphical abstract

Abstract The outbreak species, Orgyia trigotephras caused signifcant defoliation in northeastern Tunisia in 2005. This work aims to elucidate the population cycle of this pest by testing a wide range of variation of fecundity and population growth. The recorded fecundity was at its highest peak with an average of 153 eggs/egg batch during outbreaks. The action of the complex of egg parasitoid/predator associated with O. trigotephras varies over time. The action of Aprostocetus sp. and Coccidiphila rungsella was at its utmost during the collapse phase of the insect in 2007 and 2014. Only these two species were recorded over our 17-year study. A low proportion of dried eggs versus a high proportion of unfertilized eggs were observed due to the poor quality of foliage consumed by the mother larva during its development. The correlation between fecundity and unfertilized eggs was highly signifcant. Fecundity change indicators of O. trigotephras are indirect, namely defoliation by high densities of larvae reducing leaf quality for the next generation. The abundance of the host species makes it easily found by parasitoids or vulnerable to parasitism. This strategy is used by O. trigotephras since the action of natural enemies is very low. Yet, the insect was not observed since 2018. It will be important to conduct large research in the region to see whether the insect is still present in the localities or relocate to other ones near the studied site

The galls induced by cynipids in host oaks have been proposed as biodiversity hotspots. They constitute support for the development of arthropod communities of great diversity and functional complexity that find in them nutrition and protection from external abiotic and biotic elements which change according to environmental gradients. We characterize the abundance, richness, and diversity of gall-inducing cynipids associated with the galls of the host oak Quercus rugosa, through an elevation gradient. This study was conducted on 140 oak trees belonging to seven populations (20/site) in central Mexico. We identified 39 gall-inducing cynipid species (Cinipini), three inquiline species of galls (Synergini), and seven parasitoids of gall-inducing cynipid (Chalcidoidea), and the secondary fauna was characterized by eleven arthropod orders. We detected a positive and significant effect exerted by the altitudinal gradient on abundance, species richness, and diversity of gall-inducing cynipids, parasitoids, inquilines, and secondary fauna (order richness level). We documented positive and significant relationships between the gall-inducing cynipids and their parasitoids, inquilines, and secondary fauna in terms of species richness, diversity, and abundance of individuals. Arthropod community composition associated with gall-inducing cynipids differed among localities. This study suggests that gall-inducing cynipids in Q. rugosa act as ecosystem engineers that modify the host plant to offer a new habitat to other arthropods. Also, our results supported that Cynipid gall acts to protect the galls-associated arthropod community from unfavorable abiotic conditions throughout the altitudinal gradient.

Andrena vaga and Colletes cunicularius are solitary bees distributed in Europe in regions with sandy substrate. They both nest in large aggregations and often together. Both species occur in early spring and collect pollen usually from willows (Salix). We studied the pollen loads carried into nests by females of both species during the whole nesting season in one locality (Lázně Bohdaneč, Czech Republic). Additional material was collected in 24 other localities but usually not during the whole nesting season. The results showed that Andrena vaga is monolectic on Salix but C. cunicularius collected 11 pollen types, and one type usually dominated in each pollen load. The pollen of Salix represented 60% or more, especially in the second half of the nesting season, when was collected less frequently. Although C. cunicularius is certainly polylectic, individual specialisation to one pollen type was revealed during foraging bouts. The pollen diet of C. cunicularius partly corresponded with other polylectic bees in the studied locality. The main difference was pollen of Taraxacum (Cichorioideae), which was the most represented pollen type in pollen loads of polylectic bees but nearly absent in pollen loads of C. cunicularius. Andrena vaga is probably behaviourally specialised on pollen collected on Salix only and is unable to collect pollen from flowers of other plants, contrary to C. cunicularius.

Herbivore-induced plant volatiles (HIPVs) are regarded as an indirect plant defense against herbivores, since they attract natural enemies to infested plants. On the other hand, HIPVs also affect behavioral responses of herbivores. In a previous study, Lytopylus rufipes, a parasitoid of the oriental fruit moth (Grapholita molesta), showed positive responses to pear HIPVs, but the influence of pear HIPVs on G. molesta is still unclear. To better understand these responses, we first tested oviposition preferences of G. molesta to uninfested and infested pear shoots (US and IS, respectively) and uninfested mature leaves (ML) in dual-choice bioassays using a cylindrical tube. Then, preferences to volatile components were also assessed. G. molesta females preferred US-, IS-, and ML-treated areas compared to the control area (no leaves), respectively. Subsequently, G. molesta females preferred IS over US, and US more than ML in bioassays. Furthermore, G. molesta females did not show any significant preference for individual volatile components, but more eggs were laid in an area treated with a synthetic pear HIPV blend, compared to the hexane-treated area (control). These results indicate that G. molesta females do not avoid infested pear shoots nor HIPVs. Moreover, HIPVs may recruit not only natural enemies, but also G. molesta females to the release point of HIPVs. Thus, it is important to examine responses of G. molesta females to HIPVs in the field before employing them for pest management.

Tree diversity exerts strong controls on predator–prey interactions, generally boosting predation pressure and thus pest control. One of the reasons for this outcome is that carnivores are better able to respond to changes in prey location or availability with increasing plant diversity. To address this, we manipulated prey vertical location within the canopy on mahogany trees planted in monoculture and polyculture plots in a tree diversity experiment using plasticine caterpillars. We conducted three surveys of predation, estimated as the daily proportion of models attacked per tree (n = 288 trees and 3456 caterpillars). We found no effect of tree diversity on attack by birds or arthropods. There was, however, an effect of prey vertical location, with higher bird and arthropod predation rates in the mid-canopy vs. low canopy. There were no interactions between diversity and prey location, suggesting diversity did not affect predator responses to prey availability along the canopy. Finally, bird predation correlated negatively with arthropod predation, but only in polyculture, suggesting diversity influenced bird–arthropod interactions. These findings call for work assessing the mechanisms behind tree diversity effects on predator responses to prey availability to better understand of how plant community heterogeneity shapes top-down control.

Species contribute differently to the structure and stability of networks of interacting species. However, species contributions to the importance of other species is usually neglected, thus limiting our understanding of species dynamics beyond the general network structure. We combined knowledge on diversity effects on focal species and network ecology to analyze the influence of plants and herbivores on big-leaf mahogany's (Swietenia macrophylla) importance in the plant–herbivore network. To this end, we built interaction networks using information from a large-scale tree diversity experiment and performed computer simulations of species removal with redistribution of interactions. We compared the importance of big-leaf mahogany in the observed networks to simulated networks where we removed: (a) tree species with similar beetle assemblages to mahogany, (b) the most interconnected (core) tree species and (c) the core beetle species. Removal of the core and similar tree species increased the importance of mahogany, whereas eliminating core beetle species decreased it. Interestingly, the effect of core tree species on mahogany’s importance was mediated by core beetles (R² = 0.46). Neither tree nor core beetle species’ effects were contingent on tree species richness or abundance. These results indicate that highly connected tree and herbivore species jointly determine the role of mahogany in the plant–herbivore network. Likewise, these results provide insight into the effect of tree species composition and highly interactive herbivores in shaping the role of species in the herbivore network.

A wide range of ant-plant mutualistic associations are known to occur in terrestrial ecosystems. Although many species of plants recruit ants to obtain protection from herbivores, myrmecophily is rare, since only few plant species are known to be adapted for pollination predominantly by ants. The annual herb, Euphorbia hirta, is characterized by the ‘ant-pollination syndrome’ including traits such as unisexual flowers, inconspicuous cyathia clustered in globose cymes, inflorescence-associated tiny nectaries and short, semi-erect stem. In present study, we aimed to examine the pollination ecology of Euphorbia hirta and the role of ants in its pollination. Field and laboratory experiments conducted to understand the association between E. hirta plants and ants revealed that seven ant species (belonging to five genera and three subfamilies) visited E. hirta plants. The visitation patterns of ants revealed that in a single foraging trip the ants visited a number of plants indicating their potential role in cross-pollination. Field-based exclusion experiments revealed production of significantly higher number of fruits in E. hirta plants under open pollination treatment as compared to other treatments. Scanning electron microscopy revealed that the adherence of the pollen grains to the bristles located on ant mouth-parts was facilitated by the three vertical, semi-circular grooves present on the grain surface. The number of fruits produced per plant was higher in ant-included plants as compared to only winged insect-pollinated and only self-pollinated plants suggesting that the plant-visiting ants are successful pollination vectors of E. hirta and while promoting self-pollination also contribute towards cross-pollination services.