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Bagrada bug, Bagrada hilaris (Burmeister) (Hemiptera: Pentatomidae), is an invasive pest of cruciferous crops. The parasitoid Gryon aetheriumTalamas (Hymenoptera: Scelionidae) is a promising biological control agent for B. hilaris because it can forage in the soil where B. hilaris deposits most of its eggs. In this study, we assessed parasitism by G. aetherium on B. hilaris eggs in situ in northcentral California, including the Salinas Valley where most cruciferous crops in the United States are grown. Parasitism was documented by leaving soil-filled trays under infested plants for 7–14 days, then removing eggs and holding them for emergence of parasitoids. Gryon aetherium accounted for over 99% of emerged parasitoids, and occurred at 11 of the 12 sampled sites. Of the 17,729 and 31,759 B. hilaris eggs collected in 2021 and 2022, 1,518 (8.84%) and 2,654 (8.36%) were parasitized by G. aetherium, respectively. Parasitism rates were generally higher inland and ranged from 3.64% to 44.93% in 2021 and from 1.01% to 23.04% in 2022, and never exceeded 15% on any sample dates at several coastal sites in the Salinas Valley. Discovery efficiency (a measure of the ability of parasitoids to locate egg patches) reached 80% or higher at all but 1 site, but exploitation efficiency (a measure of the ability of parasitoids to exploit the egg patch after it has been discovered) was generally <20%, suggesting that G. aetherium can locate egg patches efficiently but is less efficient at finding eggs within patches.

The abundance of a widespread brood parasite, the Brown-headed Cowbird (Molothrus ater), has decreased by ∼30% in North America over the past 5 decades. Within a community, brood parasite abundance may be expected to positively correlate with host brood parasitism frequency and intensity, but evidence for this correlation is mixed. Few studies have examined if long-term changes in brood parasite abundance have resulted in changes to host parasitism frequency. We measured cowbird abundance, brood parasitism frequency and intensity of 4 riparian songbird species, and host abundance and richness in 2001–2004 and 2012–2014 in riparian vegetation of the south Okanagan Valley of British Columbia, Canada. We compared our data to historical data for the same parameters previously collected between ∼1960 and the early 1990s in the same area. We found that cowbird abundance decreased by ∼80% over 2 decades in the Okanagan Valley, mirroring or exceeding regional-scale trends. Host abundance and richness increased as cowbird abundance decreased. However, songbird brood parasitism frequency and intensity either increased or remained relatively high over more than 4 decades. We discuss possible explanations for this apparent disconnect between brood parasite abundance and host parasitism frequency and intensity, which offer opportunity for further study. Temporal changes in brood parasite abundance, such as the decline of Brown-headed Cowbirds in North America and the Common Cuckoo (Cuculus canorus) in Europe, should not be assumed to lead to correlated changes to host parasitism frequency and intensity. La abundancia de un parásito de nidadas ampliamente distribuido, el tordo Molothrus ater, ha declinado un ∼30% en Norteamérica a lo largo de las últimas 5 décadas. Dentro de una comunidad, se podría esperar que la abundancia de los parásitos de puestas se correlacione positivamente con la frecuencia e intensidad de parasitismo de puestas del hospedero, pero la evidencia al respecto es mixta. Pocos estudios han examinado si a largo plazo los cambios de abundancia de parásitos de puestas han resultado en cambios de frecuencia de parasitismo del hospedero. Medimos la abundancia del tordo Molothrus ater, la frecuencia e intensidad de parasitismo de puestas de 4 aves canoras riparias, y la abundancia y riqueza del hospedero en 2001–2004 y 2021–2014 en vegetación riparia del sur de Okanagan Valley en British Columbia, Canadá. Comparamos nuestros datos con datos históricos para los mismos parámetros colectados previamente entre ∼1960 y los inicios de 1990s en la misma zona. Encontramos que la abundancia del tordo Molothrus ater disminuyó un ∼80% a lo largo de 2 décadas en Okanagan Valley, reflejando o superando tendencias a escala regional. La abundancia y riqueza del hospedero aumentó conforme la abundancia del tordo Molothrus ater disminuyó. Sin embargo, la frecuencia e intensidad del parasitismo de puestas de las aves canoras se incrementó o permaneció relativamente alto por más de 4 décadas. Discutimos posibles explicaciones acerca de la aparente desconexión entre la abundancia del parásito de puestas y la frecuencia e intensidad del parasitismo del hospedero, que abre oportunidades de realizar futuros estudios. Cambios temporales en abundancia de parásito de puestas, como el declive del tordo Molothrus ater en Norteamérica y del cuco común (Cuculus canorus) en Europa no deben suponer cambios correlacionados en la frecuencia e intensidad del hospedero del parásito. Palabras clave: British Columbia, dinámica de poblaciones, interferencia competitiva, Okanagan Valley, parasitismo múltiple, parásitos de puestas, tasa de parasitismo.

Habrobracon hebetor (Say) is an important biological control agent for lepidopteran pests of stored products. In this study, the age-specific functional response, paralysis rate, and parasitism rate of H. hebetor under different host deprivation treatments (PC: without host deprivation, used as the control, P1d: host deprivation, but the host was removed after 1 d contact, and PW: host deprivation from beginning) were evaluated at different larval densities (5, 10, 20, 40, and 80) of the Ephestia elutella (Hübner) at 28 ± 1°C, 75 ± 5% RH and 16:8 h L:D. Ages of parasitoid females used were 2, 5, 10, and 20 d old. The logistic regression results indicated that the functional response of H. hebetor females under different host deprivation treatments was type II. The longest handling time was observed in 20-d old females, while the shortest handling time and highest maximum attack rate (T/Th) were estimated at the age of 2 d in all treatments. The paralysis and parasitism rates of H. hebetor were the highest at 2, 5, and 10-d old in all treatments. The results of this study suggest that H. hebetor females up to 10-d old can be used as an efficient biological control agent against E. elutella. The data of this study can also be used to predict the efficacy of different aged H. hebetor females in controlling E. elutella populations.

Context The alfalfa weevil Hypera postica Gyllenhal (Coleoptera: Curculionidae) is one of the most destructive pests of alfalfa worldwide. Both local and landscape-scale factors can significantly influence crop pests, natural enemies, and the effectiveness of biological control services, but the relative influence of these factors is unclear. Objectives We investigated the influence of the local variables and surrounding landscape composition and configuration on the abundance of alfalfa weevil, and on the abundance and parasitism rates of its larval parasitoids, Bathyplectes spp. Methods We sampled 65 commercial alfalfa fields along the Ebro Basin, Spain, over a period of 3 years, recording the field characteristics and landscape structure at three buffer radii of 250, 500 and 1000 m from the center of each field. Results The abundance of weevil larvae was positively associated with the field perimeter and with the uncut alfalfa surrounding the pipes of the sprinkler irrigation system, but only one configuration variable was positively correlated: the alfalfa edge density. No local characteristics or landscape structures were associated with the abundance of adult weevils. The abundance of Bathyplectes spp. adults was positively associated to local factors such as the densities of alfalfa weevils and aphids. Few landscape structure variables, such as alfalfa edge density and Simpson’s Diversity Index, had explanatory value only at 250 m buffer radius. The rate of larval parasitism was affected by local variables, such as alfalfa weevil abundance and field age. Conclusion Our results provide, for the first time in the Mediterranean region and Europe, evidence of the relative importance of landscape structure and local factors on the abundance of the alfalfa weevil and its larval parasitoids, Bathyplectes spp. The strongest influences were based on local characteristics.

Host specialization evolved in many parasite-host systems. Evolution and maintenance of host specificity may be influenced by host life-history traits, active host selection by the parasite, and host anti-parasite strategies. The relative importance of these factors is poorly understood in situations that offer parasites a choice between hosts with similar habitat requirements. The common cuckoo Cuculus canorus is a generalist parasite on the species level, but individual females prefer particular host species. In reed beds of the Yellow River Delta, China, two potential hosts with similar nest characteristics, Oriental reed warblers Acrocephalus orientalis and reed parrotbills Paradoxornis heudei, breed in sympatry. We found that warblers were parasitized at much higher rates than parrotbills. Both hosts recognized and rejected non-mimetic model eggs well, indicating that they have been involved in an arms-race with cuckoos. Cuckoo eggs closely resembled warbler eggs, and such eggs were mostly accepted by warblers but rejected by parrotbills. Only warblers recognized adult cuckoos as a specific threat. Both hosts were equally good at raising cuckoo chicks. Low nest density, partial isolation by breeding time, small scale differences in nest and nest site characteristics, and high rejection rates of natural cuckoo eggs are likely cumulatively responsible for the low current parasitism rate in parrotbills. This study emphasizes the importance of integrating the study of general host life-history characteristics and specific anti-parasitism strategies of hosts across all breeding stages to understand the evolution of host specificity.

The evolutionary processes that shape host‐parasitoid coexistence in a changing environment are poorly understood. We examined the large‐scale distribution of highly specialised polysphinctine Darwin wasps associated with spiders along an elevational gradient and tested the hypothesis that distribution and parasitism rates depend on elevation, habitat type and the species and age composition of the host community. Further, on the basis of a large‐scale dataset, we examined the hypothesis that three‐dimensional webs in spiders may be an evolutionary adaptation against polysphinctine parasitoids. We found significant variation in parasitoid distribution and parasitism rates along a 1500 m elevational gradient in central Europe. The optimal model showed a humped shape for the parasitism rate on an elevational gradient. Overall, we found relatively low parasitism rates (4%) on spiders, with the highest parasitism rates in non‐forested riparian vegetation and the lowest in agroecosystems. Rates of parasitism varied significantly among spiders forming different types of webs (foraging guilds). Spiders spinning 3D webs were dominant in the spider community, but parasitism on them was lower compared to spiders spinning 2D webs, probably because of the defensive function of the 3D web architecture. The bottom‐up approach, in which the entire spider host community is analysed for parasitism rate, supports the hypothesis that 3D webs are evolutionarily novel and could have arisen as a result of the need for defence against enemies such as parasitoids. We examined the large‐scale distribution of highly specialised parasitoids associated with spiders along an elevational gradient and tested the hypothesis that distribution and parasitism rates depend on elevation, habitat type and the species and age composition of the host community. Further, on the basis of a large‐scale dataset, we examined the hypothesis that three‐dimensional webs in spiders may be an evolutionary adaptation against polysphinctine parasitoids.

Abstract Anthonomus eugenii Cano (Coleoptera: Curculionidae) is a key pest of cultivated peppers (Capsicum species) in tropical and subtropical America. Here we evaluated the effect of five pepper varieties on the susceptibility of A. eugenii to the parasitoids Bracon sp. (Hymenoptera: Braconidae), Eupelmus cushmani (Crawford) (Hymenoptera: Eupelmidae), and Jaliscoa hunteri Crawford (Hymenoptera: Pteromalidae). Potential parasitism was estimated by comparative analysis of parasitoid ovipositor size and the depth to which host larvae develop inside the fruit. Highest potential parasitism rates were achieved by Bracon sp. and E. cushmani on árbol and habanero peppers (84–99%) while the lowest rates were achieved by J. hunteri on serrano, bell, and jalapeño (7–18%). To validate potential parasitism rates, the actual parasitism rate by Bracon sp. and J. hunteri on three varieties of peppers was assessed. Actual parasitism rates of A. eugenii larvae in árbol were similar for Bracon sp. and J. hunteri (33%), while on bell and jalapeño Bracon sp. achieved 24% and 13% parasitism and J. hunteri achieved 14% and 8%, respectively. In most cases, actual parasitism was lower than estimated potential parasitism, although the latter had a notable predictive power (predicted R2 = 0.84). Results showed that the host was more vulnerable on small-fruited varieties because larvae were closer to the pericarp and could be reached by parasitoid ovipositors; likewise, in varieties with little placenta and seed, some larvae fed in the pericarp, where they were more vulnerable.

This study assessed the parasitism rates and species composition of egg parasitoids associated with and in Northwestern Türkiye, one of the country's main hazelnut production areas. Between 2022 and 2024, a total of 15,051 eggs and 8490 eggs were collected from 65 hazelnut orchards and neighboring fruit orchards in Northwestern Türkiye. Egg masses were maintained under laboratory conditions, and emerging parasitoids were identified using morphological and molecular methods. The total parasitism rate on was 17.39%, primarily caused by (42.51%), (26.47%), (23.95%), (6.80%), and (0.27%). In the total parasitism rate was 1.98%, and all parasitoids that emerged were identified as (26.19%), (16.67%), and (15.48%). The highest discovery (24.88%) and exploitation efficiency (89.83%) for were observed for . Although native parasitoids are generally considered ineffective against due to evolutionary mismatch, their natural parasitism on eggs is promising for long-term management. The findings clarify parasitoid composition and natural parasitism patterns, demonstrating that conserving and augmenting native parasitoids can contribute to more sustainable management and reduced insecticide dependence in Turkish hazelnut orchards.

The Asian longhorned beetle (ALB), Anoplophora glabripennis (Motschulsky) (Coleoptera: Cerambycidae), is a destructive invasive woodboring insect pest, and efforts are being made to find parasitoids for ALB biological control. Through a four-year survey in Korea using a sentinel log trap associated with host chemical cues potentially important for host finding by parasitoids, two parasitoid species were discovered attacking ALB. One species is Spathius ibarakius Belokobylskij & Maetô, which is known to also parasitize citrus longhorned beetle, Anoplophora chinensis (Forster). The other parasitoid species, whose offspring were dead before imago, could not be morphologically identified at the adult stage. We attempted molecular and morphological identification of the larvae/pupae of the unidentified parasitoid; however, only superfamily-level identification was possible. The parasitism rate recovered in the logs was 0.3% by the unidentified parasitoid in Gapyeong-gun in 2019, while it reached 29.2% by S. ibarakius in Busan city in 2022. Future efforts for exploring ALB natural enemies in the pest’s native range may focus on parasitoids with high parasitism rates. Le longicorne asiatique (LA), Anoplophora glabripennis (Motschulsky) (Coleoptera : Cerambycidae), est un insecte ravageur envahissant et destructeur du bois, et des efforts sont déployés pour trouver des parasitoïdes pour la lutte biologique contre lui. Au cours d’une étude de quatre ans en Corée utilisant un piège à bûche sentinelle associé à des signaux chimiques de l’hôte potentiellement importants pour la détection de l’hôte par les parasitoïdes, deux espèces de parasitoïdes ont été découvertes attaquant le longicorne. Une espèce est Spathius ibarakius Belokobylskij & Maetô, qui est connue pour parasiter également le longicorne des agrumes, Anoplophora chinensis (Forster). Les autres espèces de parasitoïdes, dont les descendants sont morts avant l’imago, n’ont pu être identifiées morphologiquement au stade adulte. Nous avons tenté une identification moléculaire et morphologique des larves/pupes du parasitoïde non identifié, mais seule une identification au niveau de la superfamille a été possible. Le taux de parasitisme observé dans les bûches était de 0,3 % par le parasitoïde non identifié à Gapyeong-gun en 2019, tandis qu’il atteignait 29,2 % par S. ibarakius dans la ville de Busan en 2022. Les efforts futurs pour explorer les ennemis naturels du capricorne dans l’aire de répartition naturelle du ravageur pourraient se concentrer sur les parasitoïdes à taux de parasitisme élevés.

In Argentina, a classical biological control program for the Eucalyptus bronze bug, Thaumastocoris peregrinus (Carpintero & Dellapé), with the egg parasitoid Cleruchoides noackae Lin & Huber (Hymenoptera: Mymaridae) was initiated in 2014. Parasitized eggs of the pest were imported from Uruguay, and a founder colony was established under laboratory conditions. From April 2014 onwards, field releases of adult C. noackae were carried out on eucalypt trees in experimental and commercial plantations in five sites. Then, establishment and parasitism rates were analyzed through sampling of T. peregrinus eggs in spring–summer 2015 to 2020. The parasitoid was recovered in four out of the five sites studied. Four years after the parasitoid had been released, the parasitism rate reached 40% on average. This result confirmed that C. noackae was established in the field, potentially providing a tool for the biological control of T. peregrinus .