Abundance Of Parasitoids Research Articles

Assessing native parasitoids of the invasive pest Drosophila suzukii (Diptera: Drosophilidae) in the Southeastern USA.

Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), commonly known as spotted-wing Drosophila (SWD), is an invasive insect pest threatening the economy of many small fruit farms in the Americas and Europe. Biological control using parasitoids is a promising strategy for improving the sustainable management of SWD. To use the parasitoids as biocontrol agents, recognizing and understanding the presence and preference of North American native parasitoids and their local adaptation is necessary. We conducted 2 season-long field explorations of North American native parasitoids of SWD during 2021 and 2022 at major blueberry-producing locations in southeast GA, USA. A total of 371 parasitoids of Drosophila were collected using fruit-baited sentinel traps and classified into 3 families: Figitidae, Pteromalidae, and Diapriidae. Leptopilina boulardi (Hymenoptera: Figitidae) and Pachycrepoideus vindemmiae (Hymenoptera: Pteromalidae) were the most abundant species. The abundance of parasitoids was higher during the peak blueberry ripening period through the end of the harvest season compared to all other phenological stages. Out of the North American native parasitoids of SWD that we collected, Pachycrepoideus vindemmiae successfully parasitized SWD in its natural habitat, and L. boulardi only parasitized SWD larvae at a low rate of 7% in the laboratory, but it failed to emerge from all the parasitized SWD. Ultimately, we found that the existing North American native parasitoids were inadequate to suppress the SWD in these locations. Planned intervention with the classical release of Asian native specialist parasitoids in addition to the existing SWD management approaches was deemed necessary in these areas.

Missing the biodiversity for the bee: Natural land management strategies impact functional invertebrate diversity in commercial cranberry production

Abstract Simplification of agricultural environments is linked to declines in biodiversity. Improving the floral diversity within and around these areas may result in more robust and diverse ecosystems. We investigated how floral resource abundance, diversity, and species composition in a cranberry agricultural system correlated to the abundance and overall invertebrate diversity and to the abundance and diversity of specific invertebrate groups of agricultural importance (e.g. parasitoids, phytophagous taxa, pollinators and predators). This study focused on habitats immediately surrounding cranberry production and included grassy dikes under a managed system (‘dike’), and semi‐natural areas growing on the surrounding support land (‘semi‐natural’). Floral resource availability and diversity tended to be similar between habitats, while invertebrate richness, diversity and composition differed. As the availability of floral resources increased, invertebrate abundance increased but diversity decreased. Overall invertebrate community composition differed with the specific species and availability of floral resources. The habitat type and floral resource composition impacted some agriculturally important groups, as pollinator abundance was higher in the semi‐natural habitat, and parasitoid abundance varied with floral resource composition across both habitats. These results suggest that managing the structural and floral resource diversity associated with agroecosystems can help support local biodiversity. However, these systems may disproportionately benefit more common taxonomic groups. The difference in responses of individual taxonomic groups also highlights the potential tradeoffs of focusing on only a subset of biodiversity aspects.

Response of parasitoid communities to insecticide application during a Lymantria dispar outbreak in mixed oak forests

Abstract In the temperate mixed oak forests of Central Europe, outbreaks of insects such as the spongy moth, Lymantria dispar, can cause severe defoliation and insecticide is sometimes applied for their control. Parasitoids, mainly Hymenoptera and Diptera, are among the most diverse and important natural enemies of caterpillars in these forests. However, due to their cryptic lifestyle and taxonomic difficulties, we lack knowledge on the impact of insecticide applications on complex host‐parasitoid networks. In a large‐scale field experiment, we tested the effect of spraying the lepidopteran‐specific insecticide Mimic (tebufenozide) on the abundance and community composition of both adult and larval parasitoids. We combined morphological identification, DNA barcoding and metabarcoding to identify parasitoids adult or inside caterpillars, both sampled by canopy fogging during an outbreak and two subsequent years. We analysed the abundance of parasitoids, community composition and network specialisation using statistical methods that account for sample incompleteness in host‐parasitoid data. For adult parasitoid assemblages, we found strong annual effects on abundance, with highest numbers of adult parasitoids occurring in the outbreak year, as well as on annual changes in community composition, but no effect linked to insecticide application. However, the abundance and species number of immature parasitoids revealed negative effects of insecticide application, while community composition was only affected by annual variation. Coverage‐based network analyses showed a reduction of taxonomic network diversity and network specialisation associated with insecticide application in the first 2 years. Synthesis and applications: This real‐world experiment shows that parasitoid populations respond immediately to large‐scale outbreaks but only limited to local disturbances. Results indicate that this group of natural enemies exhibits high mobility, enabling them to track host populations across large spatial scales. However, our observation of reduced network specialisation after insecticide application is a warning signal that ecosystem function, and consequently natural pest control services, may be impaired by human interference at the local stand scale.

Diversity and Relative Abundance of Insect Pests and Natural Enemies in Organic Rice

A study was conducted to decipher diversity and relative abundance of insect pests, hemipteran predators and hymenopteran parasitoids in organic rice transplanted at the research farm of the Indian Institute of Rice Research, Rajendranagar, Hyderabad during Rabi, 2020. Yellow pan traps, visual count, yellow sticky traps, sweep net and D-net methods were used for collecting insect specimens. A total of 543 insect pest individuals belonging to 12 families, 678 Hemipteran predators belonging to 9 families and 2193 parasitoids of 10 families were collected. The most abundant families among insect pests, predators and parasitoids were Cicadellidae, Miridae and Eulophidae with a relative abundance of 32.41, 81.56 and 72.55%, respectively. Shannon weiner index of insect pests, predators and parasitoids was 1.81, 0.72 and 0.99 respectively. Further, Margelef diversity index of insect pests, predators and parasitoids was 1.75, 1.23 and 1.43, respectively. Furthermore, the Pielou’s eveness index was 0.73, 0.33 and 0.40, respectively. Visual count for pests, yellow sticky traps for predators and parasitoids were adjudged the most effective methods of collection.

Through the green mosaic: Different tropical vegetation types have complementary effects on parasitoid diversity and biological control in organic agroecosystems

Land use change threaten global biodiversity, impacting ecosystem services, especially in diverse tropical regions. Yet, biodiversity conservation does not guarantee ecosystem services provision, given species' variable responses to local and landscape factors. Here, we evaluate how the landscape and local resources affect parasitoid diversity and aphid biological control in a tropical organic crop. Locally, we compared parasitoid communities within the crops and on adjacent non-crop plant strips and evaluated the effect of flower resource abundance on parasitoid diversity. At the landscape scale, we analyzed the effect of natural areas and their specific vegetational types on parasitoid diversity and the scale of these effects. Finally, we evaluated the relationship between biodiversity and biological control. Non-crop plant strips had higher parasitoid species richness and abundance than the crops, but similar species composition. Flower resource abundance in the non-crop strips negatively affected parasitoid richness. Natural areas in the landscape benefited parasitoid richness at a close range (0.42 km) and reduced parasitoid abundance at a wider scale (1.75 km). Forests and savannas increased parasitoid richness and reduced abundance, while grasslands drive parasitoid abundance and may disrupt species richness. Savannah areas, where trees and grasses coexist boosted the positive effects of forests on species richness and of grasslands on abundance. Parasitoid species richness benefited biological control exclusively in communities with intermediate and high number of parasitoid species. Our findings show that natural vegetation types with different wood densities have complementary effects in parasitoid diversity in tropical agroecosystems and represent a useful baseline for development of management and zoning plans.

Temporal resource continuity for egg parasitoids of Dalbulus maidis (Hemiptera: Cicadellidae) during winter on irrigated maize crops and edge grasses.

Little is known about winter-season parasitism of eggs of the corn leafhopper Dalbulus maidis DeLong (Hemiptera: Cicadellidae), an important pest of maize throughout the Americas. Our study, conducted in Mexico, aimed to characterize winter-season parasitism of corn leafhopper eggs on maize crops cultivated with drip irrigation and on wild grasses that grow on the edges of maize crops when maize is not present. Maize leaves baited with D. maidis eggs were used to trap the egg parasitoids in the field. In the first year (2022), parasitism of D. maidis eggs was investigated in maize fields planted contiguously on different dates (asynchronous planting). In the second year (2023), parasitism of D. maidis eggs was evaluated in edge grasses and in adjacent maize crops planted on the same date (synchronous). The highest percentage of parasitism (53%), percentage of emergence, and total abundance of egg parasitoids were found in asynchronous maize fields. Here, Anagrus virlai Triapitsyn (Hymenoptera: Mymaridae), Paracentrobia subflava (Girault) (Hymenoptera: Trichogrammatidae), and Pseudoligosita sp. (Hymenoptera: Trichogrammatidae) wasps were found parasitizing the D. maidis eggs, with P. subflava being the most abundant. In wild edge grasses, only P. subflava was found, showing low levels of parasitism, while in synchronous maize, P. subflava increased its percentage of parasitism (up to 37%), percentage of emergence, and abundance, during winter. These results suggest that P. subflava acts as an efficient biological control agent of D. maidis in irrigation-grown maize crops during the winter season, and that edge grasses are overwinter habitats for P. subflava.

Manipulating the community structure of arthropods in rice fields with floral resources plants

Abstract Conservation biological control encourages natural enemies to suppress target pests through manipulation of environmental factors that influence natural enemy survival and effectiveness, including microclimates, availability of food for adults and alternative prey, and shelter from adverse environmental conditions. This study aimed to identify selective flowering plants that could be used to manipulate the arthropod community structure in rice fields. Three rice fields (a field without resources of flowering plants, a field with vegetable crop, and a field with ornamental plant) were used in this experiment. The flowering plants included Helianthus sp., Catharanthus roseus, and Cosmos sulphureus while the vegetable plants included eggplant, cucumber, and long beans. Arthropod recording was carried out by direct observation and yellow pan traps from 14 to 98 days after planting. We recorded 33,728 arthropods representing 153 species in 68 families, 13 orders, and 2 classes. The presence of flowering plant significantly affects abundance, species richness, diversity index, and evenness of arthropods both in dry and wet seasons. The rice field surrounded with ornamental plants or vegetables showed the lowest abundance of phytophagous arthropods, the highest abundance of parasitoid and predatory arthropods. Therefore, vegetable crops such as cucumber, long beans and eggplant have great opportunities as refugia in rice fields.

Entomofauna presente en refugios vegetales en un campo de vid var. Crimson Seedless en Ica-Perú

The use of chemical pesticides to control pests also affects beneficial insects, so it is necessary to implement mechanisms that allow them to be protected and promote their development. In the present investigation, three plant shelters were installed to identify their entomofauna and determine the plant species with the potential to host biological controllers of grapevine pests. The study was carried out in the 2020-21 growing season, with seven plant species to make up three plant shelters (A, B, and C) that were installed on the edges of a vineyard of the Crimson Seedless variety in Ica, Peru. In total, 1,209 insects were reported, in six orders, nine families, and sixteen species; the most abundant were pollinators, followed by phytophagous, predators, and some parasitoids. There were no statistical differences between the shelters in terms of the abundance of parasitoids and pollinators, but there were in predators and phytophagous specifically between shelters A and B with C. Shelters A and B, which included the fennel Foeniculum vulgare Mill., stood out for having a larger population of predators, including Chrysoperla externa (Hagen), the main controller of the “vine mealybug” (Planococcus spp.). The importance of plant shelters was demonstrated and their implementation in vineyards is recommended to promote biological control and contribute to integrated pest management in this crop. Keywords: biodiversity, natural enemies, conservation biological control.

Rainforest transformation reduces parasitoid wasp diversity—Can the enrichment of flowering vegetation alleviate this?

Abstract In Indonesia, the rapid expansion of oil palm and rubber plantations replaces large areas of tropical rainforest. Rainforest transformation alters the diversity and composition of parasitoid wasp communities, but appropriate management strategies to buffer their decline in rainforest transformation landscapes are not yet developed. Here, we studied the effects of rainforest conversion to smallholder rubber and oil palm plantations on parasitoid wasp species richness, abundance and species composition. We also conducted a flowering vegetation enrichment experiment using the flowering weed Asystasia gangetica in all land‐uses to investigate potential mitigation effects on parasitoid wasp diversity and composition. Rainforest transformation to rubber plantations caused a large decrease in species richness (46%) and abundance (59%) of parasitoid wasps. Community structure of parasitoid wasps differed between forest and monoculture habitats with more habitat‐specialised species in forest and a higher proportion of common species in the monoculture. The experimental flowering vegetation enrichment increased parasitoid wasp species richness by 18% and abundance by 127%. Enrichment also enhanced the presence of unique parasitoid species in plantation and furthermore increased differences in community composition between rainforest and plantations. However, the enrichment experiment was confounded by time, meaning that a multi‐year experiment with targeted controls is necessary for statistically more reliable statements. Our study shows the effect of rainforest transformation to oil palm and rubber plantations on parasitoid wasp communities. Although providing additional flowering vegetation in plantations seems to potentially mitigate diversity loss, further research is needed to confirm and to investigate the mechanisms how flowering plants alleviate negative effects of rainforest transformation on parasitoid communities. Thereby, efficient conservation strategies for parasitoids wasps and their biological control services can be developed for rapidly changing tropical landscapes.

Diversity and abundance of stink bugs egg parasitoids from organic and conventional fields in Cuba

Diversity and abundance of stink bugs egg parasitoids from organic and conventional fields in Cuba

Effects of mowing on the arthropod community in grass buffers and adjacent crop fields.

Grass buffers are commonly planted along crop borders to filter nutrient and pesticide runoff. These buffers also provide food and shelter for beneficial and herbivorous arthropods and can serve as corridors for their movement into neighboring crops. Mowing is a common maintenance practice to control woody plants in these buffers. Field experiments were conducted to determine whether mowing influences the movement of arthropods into neighboring soybean plantings (Glycine max L) and impacts their abundance in corn (Zea mays var. indentata) the following spring. Results showed that mowing had varying effects on the abundance of herbivores, saprovores, parasitoids, and predators, particularly in the grass buffers. Aerially active arthropods in the plant canopy were more adversely affected by mowing than surface-dwelling arthropods. Mowing significantly reduced grasshopper (Orthoptera: Acrididae) density in the buffers, but did not trigger their movement into adjoining soybean fields. Parasitoids, predators, and thrips (Thysanoptera: Thripidae) were dissimilarly affected by mowing, and their responses were influenced by grass type. Altogether, these findings indicate that mowing did not cause notable movement of arthropods from grass buffers into adjoining crops and had minimal effects on the community of beneficial arthropods the following spring. Also, there were no differences in the level of insect feeding injury in crop fields next to mowed and unmowed buffers.

Biorationals and Synthetic Insecticides for Controlling Fall Armyworm and Their Influence on the Abundance and Diversity of Parasitoids

Spodoptera frugiperda (fall armyworm, FAW) is a significant economic pest of maize in Uganda. Many Ugandan maize farmers employ synthetic insecticides as their main form of control despite the negative impacts of these chemicals. We tested the effectiveness of Beauveria bassiana; General Biopesticide Cocktail (mixture of B. bassiana, M. anisopliae, Isaria fumosoroseus, Lecanicillium lecani and Purporeocillium lilacanus three strains of Metarhizium anisopliae, Nimbecidine® (azadirachtin 0.03%EC), and Roket® (cypermethrin 4% and profenofos 40%); and Amdocs® (emamectin benzoate 2% and abamectin 1%) on fall armyworm and parasitoids, respectively, in 2020 and 2021. The treatments with the greatest decrease in leaf damage and infestation were Amdocs® and Roket®, followed by Nimbecidine®. The biopesticides were not always more effective than the untreated control, though; their efficacy was often lower than that of the synthetic and botanical pesticides. We recovered one egg parasitoid, Telenomus remus, and seven egg and egg-larval parasitoids (Coccygidium luteum, Coccygidium sp., Cotesia icipe, Chelonus sp., Micranisa sp., Charops cf. diversipes, and an unidentified Tachinidae). Among these, C. cf diversipes, Chelonus sp., C. luteum, C. icipe and the Tachinidae were the most abundant. Parasitism was low, averaging 10% for egg masses and 5.3% for larvae. Application of synthetic pesticides and Nimbecidine® often resulted in higher yield when compared with the untreated control. In general, a low population of parasitoids was observed. Although the parasitoid population reduced in plots treated with Amdocs® and Roket®, the percentage of parasitism of FAW was not affected. In some instances, higher yields were realized in untreated control when compared with the treated plots. Pest management practices more compatible with biological control need to be considered for the management of fall armyworm.

Diversity of Hymenopteran Parasitoids in different Crop Ecosystems

Surveys were carried out in different districts viz., Shivamogga, Davangere and Chitradurga of Karnataka to collect and document hymenopteran parasitoids parasitizing insect pests attacking different crop ecosystems. A total of 42 hymenopteran parasitoids species represented by 33 genera belonged 12 families were documented from a collection of 1379 specimens from different stages viz., egg, larva, pupa and adult stage of host insects from different host plants viz., rice, maize, cabbage, cotton, coconut, brinjal, cashew, crape jasmine, tobacco, field bean, soybean, arecanut, cocoa, okra and pongamia. Among them, maximum parasitoids species (20) were collected from larval stage of host insects with per cent species composition of 47.62. Among the families, Braconidae was found most dominant (comprised of 23.81%), followed by Eulophidae (16.67%), Encyrtidae and Scelionidae (each with 14.29%). Alpha and beta diversity were computed for the three zones. Species diversity in terms of richness, evenness and abundance of hymenopteran parasitoids were calculated and compared during study period using Shannon-Wiener index, Simpson diversity index, Margalef’s diversity index, Menhinick’s index and Evenness. Species diversity was high in Shivamogga district as evidenced by Shannon-Wiener index (2.49), Simpson diversity index (0.88), Margalef’s index (4.09) and Menhinick’s index (1.22) and Evenness (0.46), followed by Davanagere district with respect to Shannon-Wiener index (1.69) Simpson’s diversity index (0.75), Margalef’s index and Menhinick’s index (2.27 and 0.90), respectively, while evenness was 0.24 and Chitradurga district with respect to Shannon-Wiener index (1.34) Simpson’s diversity index (0.54), Margalef’s index and Menhinick’s index (2.12 and 0.59), respectively.

Forest structure and heterogeneity increase diversity and alter composition of host–parasitoid networks

Abstract Antagonistic host–parasitoid interactions can be quantified using bipartite and metanetworks, which have the potential to reveal how habitat structural elements relate to this important ecosystem function. Here, we analysed the host–parasitoid interactions of cavity‐nesting bees and wasps, as well as their abundance, diversity and species richness with forest structural elements from 127 forest research plots in southwestern Germany. We found that parasitoid abundance, diversity and species richness all increase with host abundance, a potential mediator between parasitoids and forest structure. Both parasitoid abundance and diversity increased with stand structural complexity, possibly mediated by the abundance of hosts. In addition, parasitoid abundance increased with increasing standing deadwood and herb cover. The bipartite networks of host–parasitoid interactions showed higher connectance with increasing standing deadwood, herb cover and host abundance. Analyses of interactions within the host–parasitoid metanetwork revealed that increasing host abundance and decreasing canopy cover diversify the suites of interactions present at the plot level. These results demonstrate that forest structural elements can improve the stability and resilience of host–parasitoid networks by promoting parasitoids and diversifying interactions in ecological networks.

Parazytoidy z podrodzin Pimplinae (Hymenoptera, Ichneumonidae)i Aphidiinae (Hymenoptera, Braconidae) występujące w zieleni miejskiej miasta Poznania

The study aimed to determine the species composition and abundance of parasitoids from the subfamilies Pimplinae (Hymenoptera, Ichneumonidae) and Aphidiinae (Hymenoptera, Braconidae) found in various habitats in urban greenery and to demonstrate the rela¬tionship between plant species diversity and the species structure of parasitoid assemblages. It was found that only for the subfamily Aphidiinae was there a significant effect of habitats on the abundance of individual assemblages and the effect of years on the total abundance of assemblages. A positive relationship was observed between vegetation diversity and the abundance and species diversity of parasitoids of the subfamily Aphidiinae, as well as similarity in the qualitative-quantitative structure of Pimplinae assemblages present in a given habitat. Positive effects of trees: Betula pendula, Tilia tomentosa, Salix alba and Salix caprea, shrubs: Berberis julianae, Ber¬beris vulgaris and Spiraea japonica, and herbaceous plants: Elymus repens, Festuca rubra and Hypochoeris radicata on the qualitative¬-quantitative structure of parasitoid assemblages of the subfamily Pimplinae by creating a suitable food base for these entomophagous imagines were noted.

A method for sampling parasitized Drosophila suzukii (Diptera: Drosophilidae) puparia from soil.

Methods to measure the diversity and biological control impact of parasitoids for the control of spotted-wing drosophila, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae) are being developed in support of biological control programs around the world. Existing methods to determine parasitism levels and parasitoid species composition focus on sampling D. suzukii within fresh and rotting fruit. However, many D. suzukii pupate in the soil or in dropped fruit, where additional parasitism could occur and where their parasitoids are thought to overwinter. Here we introduce a method for extracting parasitized D. suzukii puparia from the soil through a sieve and flotation system, allowing for effective collection of puparia, from which parasitoids can then be reared. Although the method considerably underestimates the absolute number of puparia in soil samples, it nonetheless yields a high number of puparia relative to sampling effort and provides a robust estimate of the relative abundance of puparia among samples. Using this method, we confirmed that at least 5 species of parasitoids, including some that have rarely been detected in past studies, overwinter in their immature stages inside D. suzukii puparia in south coastal British Columbia, Canada. The ability to sample puparia from the soil will lead to a more comprehensive view of both D. suzukii and parasitoid abundance throughout the season, help confirm parasitoid establishment following intentional releases, and provide a way to measure the diversity of parasitoid species and potential interactions among parasitoids (e.g., hyper- or klepto-parasitism) that may often occur on the soil surface.

Effects of Sweet Alyssum (Lobularia maritima) on Parasitoid and Predator Diversity and Abundance in Agroecosystems Especially in Rice

Effects of Sweet Alyssum (Lobularia maritima) on Parasitoid and Predator Diversity and Abundance in Agroecosystems Especially in Rice

Species diversity and abundance of parasitoids of fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae) from South Sumatra, Indonesia

Abstract. Herlinda S, Suwandi S, Irsan C, Adrian R, Fawwazi F, Akbar F. 2023. Species diversity and abundance of parasitoids of fall armyworm, Spodoptera frugiperda (Lepidoptera: Noctuidae) from South Sumatra, Indonesia. Biodiversitas 24: 6184-6190. The parasitoid species attacking Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) have never been reported from South Sumatra. The objectives of this research were to identify and analyze the species diversity of egg and larval parasitoids of S. frugiperda and to determine their abundance in corn fields from South Sumatra. Surveys were carried out in Ogan Komering Ilir District, Ogan Ilir District, Muara Enim District, and Palembang City. The results showed that fourteen species of parasitoids were found attacking eggs and larvae of S. frugiperda in South Sumatra. Two species were egg parasitoids (Telenomus remus (Nixon) and Trichogramma sp.), and 12 species of larval parasitoids (Chelonus formosanus Sonan, Chelonus oculator F., Chelonus annulipes Wesm., Chelonus cautus (Cresson), Microplitis manilae Ashmead, Microplitis marshallii Kokujev, Euplectrus corriemoreauae Hansson, Compsilura concinnata (Meigen), Sarcophaga sp., Macrocentrus sp., Exorista sp., and Megaselia sp.). The most abundant species of the parasitoids found was T. remus. The highest species diversity was found in Muara Enim District. The number of parasitoid species was greater in the dry season compared to the rainy season. Egg parasitism rates were significantly higher at the corn vegetative stage (59.03%) compared to the generative stage (53.56%).

High specificity of symbiont-conferred resistance in an aphid-parasitoid field community.

Host-parasite coevolution is mediated by genetic interactions between the antagonists and may lead to reciprocal adaptation. In the black bean aphid, Aphis fabae fabae, resistance to parasitoids can be conferred by the heritable bacterial endosymbiont Hamiltonella defensa. H. defensa has been shown to be variably protective against different parasitoid species, and different genotypes of the black bean aphid's main parasitoid Lysiphlebus fabarum. However, these results were obtained using haphazard combinations of laboratory-reared insect lines with different origins, making it unclear how representative they are of natural, locally (co)adapted communities. We therefore comprehensively sampled the parasitoids of a natural A. f. fabae population and measured the ability of the five most abundant species to parasitize aphids carrying the locally prevalent H. defensa haplotypes. H. defensa provided resistance only against the dominant parasitoid L. fabarum (70% of all parasitoids), but not against less abundant parasitoids, and resistance to L. fabarum acted in a genotype-specific manner (G × G interactions between H. defensa and L. fabarum). These results confirm that strong species- and genotype-specificity of symbiont-conferred resistance is indeed a hallmark of wild A. f. fabae populations, and they are consistent with symbiont-mediated adaptation of aphids to the parasitoids posing the highest risk.

Canopy hedge pruning in pecan production differentially affects groups of arthropod pests and associated natural enemies

Controlling canopy growth and size through pruning techniques in perennial agroecosystems is often crucial to maximizing productivity. However, the implications of modifying canopy architecture for arthropod management are often overlooked. We studied the effects of hedge pruning on pests and natural enemies on mature pecan trees by assessing the abundance of: 1) leaf-dwelling aphids and mites, 2) visually detectable injuries caused by black pecan aphids [Melanocallis caryaefoliae (Davis)] and Phylloxera spp., 3) aphid parasitoids and parasitized hosts (aphid mummies), and 4) predatory mites. Additionally, we assessed the prevalence of entomopathogens that dwell on the orchard floor, under the trees. Hedge pruning decreased Phylloxera infestation but increased pressure from scorch mites and the yellow aphid complex. Black pecan aphid abundance responded inconsistently, but their damage was consistently reduced in hedged canopies. Predatory mites were only affected by hedging in the second year when higher populations were observed. Although parasitoid wasp abundance was not affected by hedging, more parasitized aphids (mummies) were observed in trees that did not receive pruning in the first year. Also, higher activity of entomopathogens was observed in soil cores collected under hedged trees in the first year but lower in the second. Taken together, the effects of hedge pruning pecan canopies were case-specific, and cannot be generalized across pests or natural enemies. Nevertheless, structural and environmental variation across seasons and within hedge pruning systems clearly have implications for crop protection in pecans and other perennial systems.