Martina Falagiarda

True bugs (Hemiptera: Acanthosomatidae, Coreidae, and Pentatomidae) include harmful crop pests affecting global agriculture, with different species displaying distinct optimal conditions for development and using different habitats. Over a 2-year period, this research investigates how habitat variation and altitude can influence the species composition of true bugs and their egg parasitoids in South Tyrol (North Italy), unveiling different trends in their population and diversity across habitats: apple orchards, urban areas, and forests. A total of 25 true bug species were sampled. Urban environments hosted the highest bug abundance, predominantly driven by the invasive Halyomorpha halys , while forests showed a higher prevalence of native species such as Pentatoma rufipes and Palomena prasina . Altitude significantly influenced species composition, with H. halys and P. rufipes abundance negatively and positively correlated with altitude, respectively. A total of 12 parasitoid species (Hymenoptera: Eupelmidae, and Scelionidae) emerged from the field-collected bug eggs, including the exotic Trissolcus japonicus , predominantly associated with H. halys in urban areas. Native parasitoids exhibited higher parasitism rates on native bug species, indicating co-evolutionary relationships. The results give an insight into the ecological dynamics of local true bug species and their egg parasitoids, and highlight the value of natural and urban areas for conserving both hemipteran and parasitoid species richness and abundance.

Hymenopteran parasitoids are crucial in regulating host population dynamics and acting as natural pest control agents in agroecosystems. Despite their acknowledged importance, they are to this day largely understudied, especially concerning their community ecology. We compared communities of pentatomoid bugs, representing many pest species, and their respective egg parasitoids between farmland ecotones—comprising the initial rows of apple orchard and bordering hedges—and semi‐natural ecotones. A focus was laid on Trissolcus japonicus , an exotic and newly introduced parasitoid of Halyomorpha halys . We also investigated the total communities of hymenopteran parasitoids and potential arthropod hosts, expecting increased diversity in semi‐natural ecotones for both. Trissolcus japonicus was not detected, whereas Trissolcus mitsukurii , another exotic parasitoid of Halyomorpha halys , was found only in farmland ecotones, reflecting its host's primary distribution. Pentatomoid bugs were more abundant in farmland ecotones, while their specialized parasitoids were equally distributed between both ecotones. Arthropod richness was higher in semi‐natural ecotones, while parasitoid diversity scored higher in farmland ecotones, suggesting that farmland ecotones represent a suitable environment for diverse parasitoid communities. Furthermore, the communities of both potential hosts and parasitoids were correlated, as evidenced by parasitoid‐host co‐occurrences in both habitats. Our study emphasizes the role of different habitat types in maintaining diverse parasitoid communities and underlines the high value of hedges along field margins in agroecosystems. Further research on species–habitat networks, as well as parasitoid‐host co‐occurrences, is needed for optimizing habitat management and ensuring sustainable pest regulation.

Stink bugs are widespread agricultural pests that damage crops and reduce yield. Their impact is influenced by host plant selection and interactions with natural enemies, particularly egg parasitoids. Understanding these relationships is crucial for improving biological control strategies. This paper investigates the seasonal host plant use and parasitism of Halyomorpha halys, Palomena prasina, and Pentatoma rufipes in South Tyrol, Italy. Over two years, we conducted field surveys at 27 sites, recording stink bug presence across 85 plant species and analyzing egg parasitism rates. Results show that stink bugs exhibit distinct host plant preferences, with H. halys utilizing the broadest range of host plants while P. prasina and P. rufipes showed stronger affinities for specific families such as Sapindaceae and Rosaceae. Parasitism rates varied across species and plant families: Trissolcus japonicus predominantly parasitized H. halys while T. cultratus and two Telenomus species targeted P. rufipes and P. prasina, respectively. Spatial–temporal features and host plant associations significantly influenced species distributions and parasitoid occurrence. These findings emphasize the role of plant–insect interactions in shaping pest and parasitoid dynamics. Integrating plant diversity into pest management strategies could enhance parasitoid effectiveness and reduce stink bug populations, contributing to more sustainable agricultural practices.

BACKGROUND: Classical biological control has been identified as the most promising approach to limit the impact of the invasive pest species Halyomorpha halys (Heteroptera: Pentatomidae). This study investigated the parasitism rate at sites where the biocontrol agent Trissolcus japonicus (Hymenoptera: Scelionidae) was released and where its unintentional introduction took place, in the Trentino–South Tyrol region. The effect of land‐use composition was studied to understand which factors favor the establishment of hosts and parasitoids, including native and exotic species.RESULTS: The released T. japonicus were detected a year after the start of the program, with a significant parasitoid impact and discovery, compared to control sites. Trissolcus japonicus was the most abundant H. halys parasitoid, and Trissolcus mitsukurii and Anastatus bifasciatus were recorded also. The efficacy of T. mitsukurii was lower in sites where T. japonicus was successfully established, suggesting a possible competitive interaction. Parasitism level by T. japonicus at the release sites was 12.5% in 2020 and 16.4% in 2021. The combined effect of predation and parasitization increased H. halys mortality up to 50% at the release sites. Landscape composition analysis showed that both H. halys and T. japonicus were more likely to be found at sites with lower altitude and with permanent crops, whereas other hosts and parasitoids preferred different conditions.CONCLUSION: Trissolcus japonicus showed a promising impact on H. halys, at release and adventive sites, with minor nontarget effects, mediated by landscape heterogeneity. The prevalence of T. japonicus in landscapes with permanent crops could support IPM in the future. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

The brown marmorated stink bug Halyomorpha halys is an invasive agricultural pest with a worldwide distribution. Classical biological control has been identified as the most promising method to reduce the populations of H. halys. Adventive populations of two candidates for releases, Trissolcus japonicus and Trissolcus mitsukurii, have recently been detected in Europe. To assess their distribution and abundance, a large-scale survey was performed. From May to September 2019, a wide area covering northern Italy and parts of Switzerland was surveyed, highlighting the expanding distribution of both Tr. japonicus and Tr. mitsukurii. Within four years after their first detection in Europe, both species have rapidly spread into all types of habitats where H. halys is present, showing a wide distribution and continuous expansion. Both exotic Trissolcus showed high levels of parasitism rate towards H. halys, while parasitization of non-target species was a rare event. The generalist Anastatus bifasciatus was the predominant native parasitoid of H. halys, while the emergence of native scelionids from H. halys eggs was rarely observed. The presence of the hyperparasitoid Acroclisoides sinicus was also recorded. This study provided fundamental data that supported the development of the first inoculative release program of Tr. japonicus in Europe.

Halyomorpha halys (Stål) (Hemiptera: Pentatomidae) is an invasive alien species and a key agricultural pest. Its native parasitoids (Trissolcus japonicus Ashmead and Tr. mitsukurii Ashmead) have been registered in several countries where H. halys brought dramatic economic losses and where biological control is considered to be the most effective long-term solution. By searching for stink bug egg masses and exposing sentinel egg masses, we monitored the distribution of native and exotic egg parasitoids in Trentino-Alto Adige (Italy), an area where both the host and parasitoids are in expansion. We recorded ten pentatomids, seven parasitoid species, with the first report of Tr. japonicus in this area and a hyperparasitoid. In the assemblage, Anastatus bifasciatus (Geoffroy) and Tr. mitsukurii were the dominant parasitoids, with a different distribution in terms of context and host plants. Sycamore was the host plant where the highest number of naturally laid parasitized egg masses (26%) were recorded. Trissolcus mitsukurii showed the highest parasitism rate, and was often found in apple orchards. The emergence of exotic parasitoids showed a temporal delay compared to native ones. Sequence analysis of 823 bp of the CO1 mitochondrial gene revealed that the recovered Tr. japonicus and Tr. mitsukurii harbored one single haplotype each. These haplotypes were previously found in 2018 in Northern Italy. While sentinel egg masses proved to be very effective in tracking the arrival of exotic Trissolcus species, the collection of stink bug egg masses provided fundamental data on the plant host species. The results lend strong support to the adaptation of exotic Trissolcus species to the environmental conditions of the range of introduction, providing new information on plant host-associations, fundamental for the development of biological control programs.

In recent years, Drosophila suzukii Matsumura (Diptera: drosophilidae) caused serious damages in cherries and small fruits cultivations in South Tyrol, making it difficult for growers to continue their activities without production losses. Biological control of the pest could play an important role in its population regulation, by lowering the pest pressure at the beginning of the season. This study aims to evaluate the potential of Trichopria drosophilae Perkins (Hymenoptera: Diapriidae), an indigenous pupal parasitoid of drosophilids, in parasitizing D. suzukii in cherry orchards situated at different altitudes and characterized by different agronomic peculiarities. The release trials showed the ability of the parasitoid to find and parasitize artificially exposed pupae of D. suzukii in two out of three localities, up to 915 m. The results highlight the importance for the released species of an adequate surrounding environment for its spread and establishment.

Sustainable strategies such as classical or augmentative biological control are currently being evaluated for the long-term management of the alien invasive pest Halyomorpha halys (Stål) (Hemiptera: Pentatomidae). A three-year study carried out in northeastern Italy was performed to investigate the distribution and field performance of the H. halys egg parasitoid Trissolcus mitsukurii (Ashmead) (Hymenoptera: Scelionidae), in comparison with other parasitoid species. In the study area, adventive populations of T. mitsukurii were present since 2016, representing the earliest detection of this species in Europe. Trissolcus mitsukurii was the most abundant parasitoid and showed a higher “parasitoid impact” (i.e., number of parasitized eggs over the total number of field-collected eggs) compared to the other species, i.e., Anastatus bifasciatus (Geoffroy) (Hymenoptera: Eupelmidae), Trissolcus basalis (Wollaston) and Trissolcus kozlovi Rjachovskij (Hymenoptera: Scelionidae). The hyperparasitoid Acroclisoides sinicus (Huang and Liao) (Hymenoptera: Pteromalidae) was also recorded. Phylogenetic analysis of T. mitsukurii population distinguished two clades, one covering samples from Italy, Japan and China, the other from South Korea. The present study provides promising results for the biological control of a pest that is having a dramatic impact on a wide range of crops worldwide.

Halyomorpha halysis an invasive, widespread stink bug for which only short-term solutions are currently available for pest control worldwide. The need for long-term management solutions forH. halyshas driven studies on augmentative and classical biological control of this species, especially by its egg parasitoids. Numerous investigations in Asia, USA, and Europe on native and exotic egg parasitoids ofH. halys, and the effects on non-target pentatomids, have improved the global knowledge of parasitoid-host relationships, uncovered new associations, and led to the discovery of new species. This trend continues withAcroclisoides sinicus, a pteromalid that was described in the 1980’s from Asia. In this work we report recent findings of this species in North America and Europe. Moreover, we propose thatAcroclisoides solussyn. nov., a species described originally from the USA, is conspecific withA. sinicusbased on morphological and molecular analysis.