Predation and Parasitism of Halyomorpha halys (Hemiptera: Pentatomidae) Eggs in Minnesota

Combining Irradiation and Biological Control against Brown Marmorated Stink Bug: Are Sterile Eggs a Suitable Substrate for the Egg Parasitoid Trissolcus japonicus?

The brown marmorated stink bug (BMSB), Halyomorpha halys, is a phytophagous invasive pest native to south-eastern Asia, and it is now distributed worldwide. This species is considered to be one of the most damaging insect pests in North America and in Europe. In agriculture, the predominant approach to managing BMSB is based on the use of insecticides, specifically pyrethroids and neonicotinoids. Unfortunately, the biology of the species and its facility to develop mechanisms of resistance to available pesticides has induced farmers and scientists to develop different, least-toxic, and more effective strategies of control. In a territorial area-wide approach, the use of a classical biological control program in combination with other least-toxic strategies has been given prominent consideration. Following exploratory surveys in the native range, attention has focused on Trissolcus japonicus, a small scelionid egg parasitoid wasp that is able to oviposit and complete its larval development in a single egg of H. halys. A common method for detecting egg parasitoids in the native range involves the placement of so-called 'sentinel' egg masses of the pest in the environment for a short period, which are then returned to the laboratory to determine if any of them are parasitized. Outside of the area of origin, the use of fertile sentinel eggs of the alien species may lead to the further release of the pest species; an alternative is to use sterile sentinel eggs to record the presence of new indigenous egg parasitoids or to detect the dispersal of alien species (in this case, T. japonicus) released in a new environment to control the target insect pest species. This study evaluated the performance of three types of sterile sentinel eggs as a suitable substrate for the oviposition and larval development of the egg parasitoid T. japonicus in a context of combining classical biological control with a Sterile Insect Technique (SIT) approach.

Lateralization of Courtship Traits Impacts Pentatomid Male Mating Success—Evidence from Field Observations

Simple Summary

Although a growing number of studies have reported asymmetries of brain and behavior in various insect orders, detailed information on lateralization in the courtship and mating behavior of insects in the wild is scarce. In this research, we studied the courtship and mating behavior of the neem bug, Halys dentatus, in the field, quantifying lateralized behavioral displays, and assessing their impact on male mating success. A population-level lateralization in males approaching females was found. Furthermore, the male mating success was affected by lateralization; right-biased males achieved higher mating success rates. Overall, our results add useful knowledge on the reproductive behavior of H. dentatus in the field, with potential applications for identifying useful benchmarks to monitor the quality of individuals mass-reared for pest control purposes over time. This study furtherly highlights the role of lateralized traits in determining male mating success in insects.

Abstract

Lateralization has been documented in many insect species, but limited information on courtship and mating lateralization in wild conditions is available. We conducted field investigation on the courtship and mating behavior of the neem bug, Halys dentatus, a polyphagous insect mainly infesting Azadirachta indica, with particular attention to lateralization of mating displays. We investigated the presence of population-level behavioral asymmetries during H. dentatus sexual interactions and their influence on male mating success. Two lateralized traits were found: left or right-biased male approaches to the female and left or right-biased male turning displays. Males approaching females from their left side were mainly right-biased in the 180° turning display, and males that approached females from their right side were mainly left-biased. Right-biased males by turning 180° to carry out end-to-end genital contact, performed a lower number of copulation attempts, thus starting copula earlier than left-biased males. Mating success was higher when males approached the left side of females during sexual interactions. A higher number of successful mating interactions was observed in right-biased males when turning 180°. Our results add useful knowledge on the reproductive behavior of H. dentatus in the field, with potential applications for identifying useful benchmarks to monitor the quality of individuals mass-reared for pest control purposes over time.

Preempting the Arrival of the Brown Marmorated Stink Bug, Halyomorpha halys: Biological Control Options for Australia

The brown marmorated stink bug Halyomorphahalys (Stål) (Hemiptera: Pentatomidae) is native to Northeast Asia, but has become a serious invasive species in North America and Europe, causing major damage to crops. While it has not established itself in Australia, it has been intercepted at the border several times, indicating that future incursions and establishment are a case of when, not if. Biological control is one of the few control options for this species and will be important for managing H.halys should it become established in Australia. Prioritizing species that could be used as biological control agents would ensure Australia is prepared. This study summarizes the literature on natural enemies of H. halys in its native and invaded ranges and prioritizes potential biological control agents of H.halys that could be used in Australia. Two egg parasitoid species were identified: Trissolcusjaponicus (Ashmead) and Trissolcusmitsukurii (Ashmead) (Hymenoptera: Scelionidae). Future efforts to develop biological control should focus on T. mitsukurii, as it is already present in Australia. However, little is known about this species and further work is required to: (1) assess its potential effectiveness in parasitizing H. halys, (2) determine its current distribution and (3) host range in Australia.

Seasonal Abundance and Diversity of Egg Parasitoids of Halyomorpha halys in Kiwifruit Orchards in China

To develop effective and targeted biocontrol tactics for the brown marmorated stink bug, Halyomorpha halys, in crop habitats, a good understanding is essential of the abundance and diversity of its parasitoids in different crop habitats in its native range. To obtain information on the egg parasitoid communities of H. halys in kiwifruit, surveys using sentinel egg masses were conducted in 2018 and 2019. These assessed the species composition of egg parasitoids of H. halys in green-fleshed 'Hayward' kiwifruit orchards, and quantified their season-long abundances in orchards under two different management systems. Parasitism was observed from June to August 2018 (mean parasitism: 48%) and from May to August 2019 (mean parasitism: 29%) across the experimental orchards. In total, five different parasitoid species were found across the two surveys seasons in the kiwifruit orchards, Trissolcus japonicus, T. cultratus, T. plautiae, Anastatus japonicus, and Acroclisoides sp., where T. japonicus and T. cultratus were the predominant species. Monthly T. japonicus abundance data had a unimodal distribution in 2018, peaking in July. There were two peaks (May-June and August) in the 2019 season. Overall, T. japonicus was significantly more abundant in the organic orchard than the conventionally managed orchard only in 2018, and its monthly abundance differed significantly in the two orchards in the two survey seasons. Results and their implications for future classical biological control for H. halys in kiwifruit are discussed.

Parasitism of Adult Pentatomidae by Tachinidae in Soybean in the North Central Region of the United States

Stink bugs (Hemiptera: Pentatomidae) are agricultural pests of increasing significance in the North Central Region of the United States, posing a threat to major crops such as soybean. Biological control can reduce the need for insecticides to manage these pests, but the parasitism of stink bugs by Tachinidae (Diptera) is poorly characterized in this region. The objective of this study was to evaluate the rate of parasitism of stink bugs by tachinids over 2 yr from nine states across the North Central Region. Parasitism was assessed by quantifying tachinid eggs on the integument of stink bug adults. Parasitism rates (i.e., percent of adult stink bugs with tachinid eggs) were compared across stink bug species, states, stink bug sex, and years. The mean percent parasitism of stink bugs by tachinids was about 6% across the region and did not differ among stink bug species. Mean percent parasitism was significantly higher in Missouri than in northern and western states. In addition, male stink bugs had significantly higher mean percent parasitism than females. Stink bug species commonly found in soybean in the region showed some parasitism and are therefore potentially vulnerable to oviposition by these parasitoids. This is the first study to characterize the level of parasitism of stink bugs by tachinids across the North Central Region.

Natural Enemy Community Composition and Impact on Brown Marmorated Stink Bug (Hemiptera: Pentatomidae) Eggs in Minnesota Apple Orchards

Halyomorpha halys is an invasive, polyphagous insect that feeds on many major crops, including apple. Statewide monitoring in Minnesota has shown continued increase of H. halys populations and occurrence of this pest in apple orchards. Potential arthropod natural enemies of H. halys and other pests have not been studied in Minnesota apple orchards. The purpose of this study was to characterize the composition of natural enemy communities; compare their abundances, richness and diversities between apple cultivars using different sampling methods; and assess the impact of natural enemies on sentinel eggs of H. halys in Minnesota apple orchards. Sampling occurred during the summers of 2017 and 2018 on Zestar! and Honeycrisp cultivars in four different apple orchards. In vacuum samples, arachnids, neuropterans, and coccinellids had the highest relative abundances. On yellow sticky traps, anthocorids were the most abundant. The total predator abundance differed between the cultivars sampled across years, with more predators found on Zestar! compared with Honeycrisp. No differences were observed in richness or diversity between cultivars with the exception of yellow sticky traps in 2017, which showed a greater diversity of predators in Zestar!. Despite the abundance of natural enemies sampled, sentinel egg masses deployed in the orchards each summer suffered on average <2% predation and no parasitism across years. Knowledge of differences in predator abundance between cultivars could inform management decisions; however, with current management practices, the potential for biological control of H. halys in conventional apple orchards appears low.

Impact of Temperature Storage Conditions of Halyomorpha halys (Hemiptera: Pentatomidae) Eggs on Parasitism by Anastatus reduvii (Hymenoptera: Eupelmidae)

Brown marmorated stink bug, Halyomorpha halys Stål, is an invasive species of Asian origin that is an important agricultural pest in the eastern United States. Sentinel egg masses are tools used to assess the impact of natural enemies on H. halys populations. To determine the effect of host egg age and storage conditions on their susceptibility to parasitism, H. halys eggs were stored at different temperatures for different lengths of time and then exposed to Anastatus reduvii (Howard), a native natural enemy of H. halys occurring in eastern North America. For eggs stored at 15, 20, and 25°C and then exposed to A. reduvii, the number of host eggs from which parasitoid offspring emerged declined with age of eggs. Control eggs (exposed to parasitoids without being stored) and those eggs stored for only 5.5 degree-days (DD) (=0.5 days) at 25°C yielded the highest percentage of parasitoids at 88.2 and 88.3%, respectively. For eggs stored at 20 and 25°C for 7.3 DD to about 36 DD, offspring emerged from about 58 to 73% of eggs, and total parasitism (emerged + unemerged parasitoids) ranged from about 70 to 80%. Parasitoid emergence was significantly lower for host eggs stored at 15°C for comparable times at 20 and 25°C. Stink bugs nymphs hatched from <0.6% of all eggs. Parasitoid-induced host egg abortion was an important component of egg mortality caused by A. reduvii, with underdeveloped stink bug nymphs, undifferentiated cell contents, and parasitoid host feeding occurring across all storage treatments.