Parasitoid Community Research Articles

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.

Multi-habitat landscapes are more diverse and stable with improved function

Conservation, restoration and land management are increasingly implemented at landscape scales1,2. However, because species interaction data are typically habitat- and/or guild-specific, exactly how those interactions connect habitats and affect the stability and function of communities at landscape scales remains poorly understood. We combine multi-guild species interaction data (plant–pollinator and three plant–herbivore–parasitoid communities, collected from landscapes with one, two or three habitats), a field experiment and a modelling approach to show that multi-habitat landscapes support higher species and interaction evenness, more complementary species interactions and more consistent robustness to species loss. These emergent network properties drive improved pollination success in landscapes with more habitats and are not explained by simply summing component habitat webs. Linking landscape composition, through community structure, to ecosystem function, highlights mechanisms by which several contiguous habitats can support landscape-scale ecosystem services.

The relative influence of agricultural abandonment and semi-natural habitats on parasitoid diversity and community composition.

Wild biodiversity is usually larger in semi-natural habitats than in croplands, but this pattern is not ubiquitous because it varies among taxa and geographic regions. Knowing how the diversity of natural enemies is structured at the landscape level is important to better understand when semi-natural habitats promote the conservation of natural enemies and ultimately enhance biocontrol. We explore the relative influence of agricultural abandonment and the proportion of semi-natural habitats at the landscape level on the diversity and abundance of parasitoid wasps in the Ichneumonidae family. We studied changes in parasitoid diversity both at local and regional scales (i.e. alpha vs beta diversity), and both at the taxonomic and functional level (i.e. species vs guild identities). We extracted landscape features in circular buffers of varying radii to perform a multi-scale analysis, and to assess at which scale landscape-level effects influenced parasitoid assemblages. We found that parasitoid alpha and beta diversity decreased with an increasing proportion of semi-natural habitats. The multi-scale analysis revealed that for this group of natural enemies, landscape-level effects occur at mid to low distances (i.e. less than 500m). Our results provide insights into the origin of pest natural enemies, their spillover to croplands, and may help to understand under which circumstances semi-natural habitats fail at promoting biocontrol services.

Network structure and taxonomic composition of tritrophic communities of Fagaceae, cynipid gallwasps and parasitoids in Sichuan, China

Abstract A key question in insect community ecology is whether parasitoid assemblages are structured by the food plants of their herbivore hosts. Tritrophic communities centred on oak‐feeding cynipid gallwasps are one of the best‐studied tritrophic insect communities. Previous work suggests that host plant identity is a much stronger predictor of oak–cynipid interactions than of cynipid–parasitoid interactions. However, these relationships have not been formally quantified. We reason that the potential for ‘bottom‐up’ effects should increase with host plant phylogenetic diversity. We, therefore, generated quantified interaction network data for previously unstudied tritrophic cynipid communities in Sichuan, China, where, in addition to Quercus, cynipid host plants include Castanea, Castanopsis and Lithocarpus. We characterise these communities taxonomically and compare the extent to which host plant taxonomy predicts plant–herbivore and plant–parasitoid associations. We sampled 42,620 cynipid galls of 176 morphotypes from 23 host plant species, yielding over 4500 specimens of 64 parasitoid morphospecies. Many parasitoids were identifiable to chalcidoid taxa present in other Holarctic oak cynipid communities, with the addition of Cynipencyrtus (Cynipencyrtidae). As elsewhere, Sichuan parasitoid assemblages were dominated by generalists. Gallwasp–plant interaction networks were significantly more modular than parasitoid–plant association networks. Gallwasps were significantly more specialised to host plants (i.e. had higher mean d' values) than parasitoids. Parasitoid assemblages nevertheless showed significant plant‐associated beta diversity, with a dominant turnover component. We summarise parallels between our study and other Fagaceae‐associated cynipid communities and discuss our findings in light of the processes thought to structure tritrophic interactions centred on endophytic insect herbivores.

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.

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.

Hyperparasitic showdown: <i>Sclerodermus cereicollis</i>, a non-aggressive but surprisingly secondary hyperparasitoid

This study investigates the dynamics of hyperparasitism within the Bethylidae family, focusing on the interaction between Sclerodermus cereicollis and Goniozus legneri, two parasitoid wasp species characterized by different sociality and aggressivity towards conspecifics. Experimental trials were conducted using Corcyra cephalonica larvae as hosts, with different setups to stimulate competition. The results revealed unexpected behaviors, especially by S. cereicollis, including aggressive interactions, cannibalism, and hyperparasitism. In contrast, despite the typically aggressive nature of G. legneri, no particular hostility was observed toward S. cereicollis. The study highlights the complex dynamics of competition for resources among parasitoids, shedding light on the adaptive strategies and fitness costs associated with hyperparasitism. These findings contribute to a deeper understanding of the ecological interactions within parasitoid wasp communities.

The cynipid gall wasp Diplolepis rosae is more successful in North America than in Europe because of enemy release

Abstract The Enemy Release Hypothesis predicts that introduced species in their new range are freed from natural enemies (e.g., pathogens, parasitoids and predators) that control their populations. Diplolepis rosae (Hymenoptera, Diplolepididae), native to the Western Palearctic, induces readily apparent galls on wild roses (Rosa spp.) that support a robust component community of inquilines, parasitoids and hyperparasitoids in its native range. D. rosae was introduced to North America in the mid‐1800s, and has since become widespread and common across the continent. We compared the insect communities associated with D. rosae galls from Canada and the US Pacific Northwest with those of Eastern Europe. Throughout its introduced range, parasitism rates were lower compared with galls in their natural range. Component communities were also less diverse and species‐rich. The relationship between gall size and parasitism rates showed no significant difference between the two continents. These results show that the component community in its introduced range is depauperate and provide support for the Enemy Release Hypothesis.

Community structure of parasitoids attacking Schizomyia sasakii (Diptera: Cecidomyiidae) and local adaptation of the gall midge in the Izu region

AbstractInsect community structures and biological interactions vary with the distance from the mainland to islands. Gall inducers are key organisms in local arthropod communities because their galls harbor diverse arthropods. We investigated the parasitoid community of a gall‐inducing cecidomyiid Schizomyia sasakii on the Izu Peninsula and the Izu Islands, Japan. We examined relationships between parasitism by Inostemma sp. and Torymus hirtipennis, and gall characteristics, and analyzed the directional selection on gall characteristics induced by S. sasakii in each locality. The species richness of parasitoids on the Izu Islands decreased with the distance from the Izu Peninsula to each island, and area of respective islands. Inostemma sp. preferably attacked large galls on Ohshima Island, and T. hirtipennis tended to attack relatively small galls in the Izu Peninsula. Directional selection on gall characteristics of S. sasakii favored the induction of larger galls and thicker tissues by S. sasakii on Ohshima Island. In contrast, no directional selection was detected in the gall characteristics on Hachijojima Island. The number of alternative host species of parasitoid may affect variation in parasitoid richness of S. sasakii on distant and small islands, because the species richness of gall midges is necessary to maintain local parasitoid populations. Our study supported the ovipositor limitation hypothesis for the torymid species, related to gall size. The directional selection of parasitoid attacks on the Izu Islands may act to favor the induction of large and hypertrophic galls by S. sasakii to avoid the parasitoids.

Temporal changes in the composition of parasitoid assemblages associated with the invasive chestnut gall wasp

Abstract Invasive alien species pose a challenge to ecosystem stability and crop production, so understanding their interactions with the natural communities they invade is crucial to mitigate negative effects. The oriental chestnut gall wasp, Dryocosmus kuriphilus Yasumatsu (Hymenoptera: Cynipidae), is an invasive insect that attacks chestnut trees. It was first recorded in Spain in 2012 and is now presumably present in the majority of chestnut stands in the country. We assessed variation in the abundance of D. kuriphilus galls and the composition of their associated parasitoid community (Hymenoptera: Chalcidoidea) during a 4‐year period (2014–2017) in 12 sampling sites in Catalonia (Spain, northeastern Iberian Peninsula), and identified which species contributed most significantly to the control of D. kuriphilus. The results show that the abundance of individual parasitoid species varied during the study period and that the number of species increased year after year. There was also a transition in the parasitoid community composition across the years. Our data suggest that the joint action of the non‐native parasitoid Torymus sinensis Kamijo and the native T. notatus (Walker) (Hymenoptera: Chalcidoidea: Torymidae) led to the decline of D. kuriphilus until it was no longer considered a pest. Also, the observed pool of parasitoid species ended up being relatively homogeneous across sites over the years, which may be due to the high natural dispersal of these parasitoids (both by active flight and passive wind dispersal).

Population dynamics of Palpita forficifera Munroe, 1959 (Lepidoptera: Crambidae) and associated parasitoids in olive orchards.

Palpita forficifera Munroe, 1959 (Lepidoptera: Crambidae) is the main pest of the olive tree (Olea europaea L., Oleaceae) in Brazil and its management has been difficult, as there are few products recommended for its control. This study aimed to evaluate the population dynamics of P. forficifera and the entomofauna of parasitoid eggs and larvae in three olive orchards under different cultivation systems, in Rio Grande do Sul state, Brazil. The study was carried out from October to May, in the 2017/18 and 2018/19 harvests, in olive orchards of different cultivars in the municipalities of Pelotas and Rio Grande, state of Rio Grande do Sul, Brazil. Population dynamics of P. forficifera varied according to the agricultural season, the months sampled, and the orchards (sites) evaluated. The highest infestation reached around 60% of the shoots in some months, depending on the orchard evaluated. During the pest infestation period, the occurrence of the egg parasitoid Trichogramma foersteri Takahashi, 2021 (Hymenoptera: Trichogrammatidae) was observed along with three larval parasitoids belonging to the genera Dolichogenidea Viereck, 1911, Hymenochaonia Dalla Torre, 1898 (Hymenoptera: Braconidae) and Temelucha Förster, 1869 (Hymenoptera: Ichneumonidae). Temelucha hilux Gauld, 2000 is recorded for the first time in association with a host, and its distribution in the country is extended to the southern region, from Brazil. Due to the scarcity of information on pest management, the natural occurrence of natural enemies in crops is of paramount importance in helping to manage P. forficifera in the field. The population dynamics of P. forficifera is also influenced by the parasitoid community, made up of at least four species of parasitic Hymenoptera. Therefore, strategies aimed at managing P. forficifera must be well developed in order to maintain and increase natural biological control in the field.

Lifecycle of Dryocosmus kuriphilus Yasumatsu and Diversity and Importance of the Native Parasitoid Community Recruited in the Northern Region of Portugal.

In this work, the objective was to learn the life cycle of D. kuriphilus and the diversity of native parasitoids in the northern region of Portugal between 2017 and 2019. The places studied belonged to the regions of Entre-Douro-e-Minho, Beira Interior, and Trás-os-Montes. To achieve the proposed objectives, buds were collected for egg and larva observation, galls were collected for larva, pupa, and adult observation and monitoring, and emergency boxes were used to identify the fauna present in the galls. In this study, 92% of D. kuriphilus adults emerged between June and July, with emergences occurring until September. We also obtained adults in winter, so it is important to study, in future works, the hypothesis of this pest performing diapause. Regarding the study of native parasitoids, compared to other countries, the same families emerged, with good rates of natural parasitism, although with fluctuations over the years. In the three municipalities under study, 11 species were identified (Eupelmus azureus Ratzeburg, Eupelmus urozonus Dalman, Eurytoma brunniventris Ratzeburg, Megastigmus dorsalis (Fabricius), Ormyrus pomaceus (Geoffroy), Sycophila iracemae Nieves Aldrey, Sycophila variegata (Curtis), Sycophila biguttata (Swederus), Torymus flavipes (Walker), Torymus auratus (Mueller), and Torymus notatus (Walker)). The average parasitism rates varied between 1.92% and 10.68%.

Potential Parasitoids for Biocontrol of the Ber Fruit Fly, Carpomya vesuviana Costa (Diptera: Tephritidae).

The ber fruit fly (BFF), Carpomya vesuviana Costa, 1854 (Diptera: Tephritidae), is an important key pest of the jujube, Ziziphus jujuba Miller. The main control measures against this pest are to use chemical control, but the first survey for its natural enemies was performed in Iran. Here, we report eight species of parasitic wasps of the BFF from five different families. The family Eurytomidae with three species, the families Pteromalidae and Mutillidae with two species each, and the families Braconidae and Diapriidae with one species each are associated with different immature stages of the BFF, of which Eurytoma pineticola Zerova (Eurytomidae) and Cyrtoptyx lichtensteini (Masi) (Pteromalidae) were the most abundant parasitoid species. Fopius carpomyiae (Silvestri,) was not reared on BFF on the jujube during this survey, but it was reported on Ziziphus spina-christi (L.) with a high parasitism rate. Therefore, it seems to be the most important parasitoid of BFF in Iran. The parasitoid community of BFF in Khorasan, Eastern Iran, is reviewed, and an identification key to these species is proposed.

Factors shaping the abundance of two butterflies sharing resources and enemies across a biogeographic region

AbstractAimIntraspecific variation in species relative abundance is shaped by a complex interplay of abiotic and biotic factors, making it both necessary and challenging to assess their combined relative importance in explaining variations across space and time. We used two congeneric butterfly species for which extensive count data and a deep understanding of their natural history is available to test three hypotheses explaining intraspecific variation in their abundance: (H1) seasonal dispersal behaviour driven by climate, (H2) resource availability and (H3) apparent competition mediated via shared parasitoids.TaxonGonepteryx rhamni (Brimstone) and G. cleopatra (Cleopatra).LocationNE Iberian Peninsula, where both species coexist, and a nearby archipelago (Balearic Islands), where only Cleopatra occurs.MethodsWe analysed spatial abundance variations for both species in the mainland and island–mainland differences in the abundance of Cleopatra. Abiotic and biotic factors, including temperature, host plant and overwintering habitat availability, larval parasitism and density dependence, were tested to explain the observed variations.ResultsH1 can explain variation in butterfly abundance between mainland regions since in warmer summers populations increased in cooler areas but decreased in warmer areas. H2 explains the variation within mainland climate regions with a strong positive relationship between resource availability and abundance but is unlikely to explain the island–mainland variation in the abundance of Cleopatra. H3 could neither explain biogeographical variation in abundance because although richer parasitoid communities were found on the mainland, larval mortality rates were similar or lower on the mainland than in the islands.Main ConclusionsClimate and resource availability jointly account for variation in butterfly abundance across the mainland, but neither these factors nor parasitism can explain island–mainland differences. Both coexisting butterfly species and their larval parasitoids may have undergone evolutionary processes, resulting in spatial segregation that promotes the coexistence of the two butterfly species on the mainland.

Diversity of parasitoid wasps (Insecta, Hymenoptera) in oilseed rape fields in Serbia

Oilseed rape is an important crop grown worldwide and used for various purposes, including oil extraction and animal feed. In Europe, there are six major pest species and several other minor pests that can significantly affect oilseed rape production, requiring growers to effectively control them in order to ensure crop yield. The host-parasitoid complexes of these pests have been studied in detail and recorded mainly in western, central and northern Europe. As an abundant source of pollen and nectar, oilseed rape may also be attractive to other parasitoids that do not have direct trophic interactions with oilseed rape pest species. The aim of this study is to fill the knowledge gap regarding the wider parasitoid community in oilseed rape fields, particularly in southern Europe. During the two-year study, a total of 3135 specimens of primary and secondary parasitoids were sampled, of which 2855 were found in oilseed rape fields and 280 in semi-natural habitats. We found 153 taxa, of which 119 were found in oilseed rape fields and 87 in semi-natural habitats. We identified 31 genera (33 species) as parasitoids of oilseed rape pests, 54 genera (97 species) parasitising non-pest species and 10 genera (23 species) as possible parasitoids of oilseed rape pests. This study shows that the parasitoid community in oilseed rape fields is very diverse and that includes parasitoids of both oilseed rape pest and non-pest species.

Bottom‐up effects shift top‐down community structure of the parasitoid guild that attacks Asphondylia borrichiae (Diptera: Cecidomyiidae) on Borrichia frutescens (Asteraceae)

Abstract Asphondylia borrichiae induces galls at the apical meristems of its host plant, Borrichia frutescens, and the larvae develop and pupate within the gall. During development, immature stages of the midge are attacked by four species of parasitic wasps; two of these parasitoids, Galeopsomyia haemon and Torymus umbilicatus, are the most common members of the guild, and both are hyperparasitic. In the current study, plots of B. frutescens were randomly assigned to control (unmanipulated), salted or fertilised in a long‐term press experiment. Although plots initially exhibited no differences in stem length, gall and flower densities, after 3 months, they began to exhibit significant differences, suggesting stress (salted plots) and vigour (fertilised plots). Galls produced on plants from fertilised plots were approximately 20% and 31% larger than those from control and salted plots, respectively. Larger gall diameter in fertilised plots resulted in a shift of the parasitoid community towards the largest parasitoid, T. umgbilicatus, whereas smaller galls produced in salted plots became biased towards the smallest, but gregarious, G. haemon; interestingly, this pattern held for T. umbilicatus across treatments, and the effect for G. haemon was not significant when all treatments were combined. This study suggests that abiotic factors that alter host plant characteristics, such as gall diameter, affect the composition of the parasitoid guild that attacks A. borrichiae, which has implications for the acquisition of enemy‐free space during host range expansion of the midge.

Geographical variation in parasitoid communities and the cause of enemy-free space in a range-expanding myrmecophilous lycaenid butterfly

Abstract Range expansions of host species are likely to modify host–parasitoid interactions. Observational studies have indicated that host species in recently colonized areas are less frequently attacked by parasitoids; however, these studies did not determine whether traditional parasitoids can still use host populations in these areas. Thus, it is unclear why the host has escaped from their traditional parasitoids in their recently colonized areas. In this study, we examined the interaction between myrmecophilous lycaenid butterfly, Arhopala japonica, and its larval parasitoids in northern Japan, a recently colonised area. This region corresponds to a distribution of A. japonica, a myrmecophilous lycaenid butterfly. No parasitoids emerged from A. japonica larvae collected in the north, whereas six parasitoid species attacked the host larvae in native areas. Attacks from the braconid wasp Cotesia sp. near inducta were the most common; however, parasitism tests revealed that Cotesia sp. near inducta and other parasitoid species completed their development successfully regardless of origin of their butterfly hosts. Population genetic analyses supported the recent range expansion of both A. japonica and Cotesia sp. near inducta. These results suggest that both hosts and parasitoids have experienced recent population expansion; however, the more rapid range expansion of A. japonica has caused escape from the enemy in newly colonized areas.

Galling insect communities mediate the effects of fire on their associated parasitoid communities

Abstract Understanding fire effects on multitrophic levels is critical to the context of changes in fire regime and climate. Insects located at higher trophic levels, like parasitoids, are more vulnerable to habitat changes than insect herbivores because they need well‐established populations of their hosts to survive. Currently, fire effects on parasitoids and their interactions with their hosts are unknown. Our aim was to study the changes in abundance, richness and species composition, as well as the food web structure in a system involving parasitoids and galling insects under different fire scenarios. We asked whether potential changes in abundance, species richness and composition of parasitoid communities are explained by galled plant abundance, species richness and composition of galling insects, and how fire affects the structure of galling insect–parasitoid food webs. The highest parasitoid richness was found in the 9 years after fire scenario, whereas parasitoid abundance was not affected by fire. The parasitoid species composition in the 9 years after fire scenario was different from that in the unburned and 3 years after fire scenarios. Parasitoid communities were modulated by galled plant abundance, species richness and composition of galling insect communities. Vulnerability was significantly higher in 9 years after fire scenarios, but it increased with increasing network size. Fire affects the community of parasitoids through changes in their host communities. Differences in exclusivity to fire scenarios and diet specialisation of parasitoid species and galling insect richness may explain the patterns found. Our study supports evidence that fire creates habitats heterogeneous in the availability of hosts shaping the parasitoid communities, with a bottom‐up effect in food webs. Additionally, in burned areas were recorded unique galling insect–parasitoid interactions.

The relationship between host plant traits and biodiversity across three sympatric seed‐feeding tri‐trophic systems in a tropical region of Brazil

Abstract We describe the diverse community of insect herbivores and parasitoids associated with the seeds and fruits of three sympatric Fabaceae species in Lavras, Minas Gerais, Brazil: Inga vera, Senna multijuga and Leucaena leucocephala. A total of 5353 individual insects, representing 77 different species, were identified via morphology and DNA barcoding. The non‐native L. leucocephala had the least diverse natural enemy community (N = 17 species), while two native species, I. vera and S. multijuga, were more diverse (N = 40 and N = 24 species, respectively). Individuals from the insect order Hymenoptera, a group dominated by parasitoid wasps, were the most diverse recovered from our samples in all hosts. Additionally, individual herbivore and parasitoid species were more likely to be found on a single host, with only four out of the 77 species found in more than one plant species. This includes the generalist agricultural pest herbivore, Lasioderma serricorne, found in two species, and three parasitoids connecting native S. multijuga and non‐native L. leucocephala communities, hinting at recent host shifts. Furthermore, different host plant traits had complex effects on the herbivore and parasitoid communities, where seed number per fruit promoted a propagating effect on the abundance and richness at both higher trophic levels, whereas seed and fruit weight did not. We highlight the importance of including parasitoids in insect community studies because they are highly diverse and provide important ecosystem services. Additional study of the biology, behaviour and distributions of parasitoids would be advantageous to inform conservation and biological control.

Pre-egg hatch efficacy of dormant applications against Lymantria dispar (Lepidoptera: Erebidae).

Lymantria dispar L. is an invasive, non-native defoliating Lepidopteran established in North America that feeds on forest and urban trees. While many products are available to manage L. dispar post-emergence, few exist to prevent egg hatch when applied to egg masses. Here, we present the results of 3 separate experiments aimed at determining the efficacy of pre-emergent insecticides against L. dispar egg hatch. We found that the labeled rate (1:1) of Golden Pest Spray Oil (GPSO; AI: 93% soybean oil) can prevent L. dispar larvae from emerging in both field and lab assays. In large public spaces, we found that this treatment was ineffective at preventing L. dispar emergence or defoliation. Acelepryn (AI: 18.4% chlorantraniliprole) resulted in some suppression of egg hatch at a very low rate (.06 ml/ 3.8 liter) in both lab and field settings and the efficacy of higher rates should be further investigated. We also tested GPSO against Lepitect (97.4% acephate) in a public area that also received a Foray 48B (12.65% Bacillus thuringiensis, subsp. kurstaki) aerial application. On large oak trees in public areas, GPSO and Lepitect were not effective at reducing defoliation. Dormant pesticide applications generally reduce the risk of affecting negatively predator and parasitoid communities and are therefore desirable. Lymantria dispar pre-egg hatch applications will not work in every situation but should be considered as part of an integrated pest management (IPM) strategy for individual homeowner trees where thorough coverage can be obtained.