The brown marmorated stink bug, Halyomorpha halys (Stål) (Hemiptera: Pentatomidae), is an invasive agricultural and nuisance pest in the United States and an increasing number of countries abroad. In the absence of other long-term solutions, biological control presents one of the most promising H. halys management options. An adventive population of Trissolcus japonicus (Ashmead) (Hymenoptera: Scelionidae), one of the most effective egg parasitoids of H. halys in their shared native range in Asia, was discovered in the Maryland in 2014 and in Frederick County, VA in 2015. Adventive populations of T. japonicus have also been detected recently in several other states and show strong indications of ongoing range expansion. Despite their importance, the foraging ecology of H. halys and especially of T. japonicus in the USA need further study. Small pyramid traps baited with a low-dose H. halys aggregation pheromone lure and deployed as vertical transects in the canopy of female tree of heaven (Ailanthus altissima (Mill.) Swingle), male tree of heaven, or hackberry (Celtis occidentalis L.), captured significantly more H. halys adults and nymphs near the top of the canopy than at mid- or lower canopy, regardless of host plant. The majority of H. halys egg masses collected via destructive sampling of felled tree of heaven were from mid-canopy, and the majority of those parasitized by T. japonicus were also from mid-canopy, with no T. japonicus emergence from egg masses collected from the lower canopy. A comparison of sentinel H. halys egg masses and yellow sticky traps deployed as vertical transects in tree of heaven revealed that the majority of T. japonicus detections occurred at mid-canopy and that while both methods proved to be equally effective, yellow sticky traps were more efficient for this purpose. This led to the development of a novel T. japonicus sampling method in which a yellow sticky trap is deployed atop a bamboo pole in the mid-canopy of wild host trees. This method was employed to compare the effect of habitat type on T. japonicus captures in female tree of heaven growing in spatially isolated patches, thin windbreaks, and at the edge of contiguous woodlots. Consistent habitat effects on T. japonicus detections were not found between sampling years, but provided the first documentation of the seasonal activity of T. japonicus in the USA. A study of host plant effects on T. japonicus detection in mid-canopy yellow sticky traps did not reveal consistent host plant effects on captures. These data provide important insights into the foraging ecology of H. halys and T. japonicus in the USA, as well as efficient sampling methods for future studies of T. japonicus. / Doctor of Philosophy / The brown marmorated stink bug, Halyomorpha halys (Stål) (Hemiptera: Pentatomidae), is an invasive agricultural and nuisance pest from Asia that is widely distributed in the United States and is present in an increasing number of countries abroad. In the absence of other long-term management solutions, biological control via the actions of natural enemies presents a promising brown marmorated stink bug management option. Trissolcus japonicus (Ashmead) (Hymenoptera: Scelionidae), also known as the samurai wasp, is one of the most effective egg parasitoids of brown marmorated stink bug in Asia. Samurai wasp arrived in the USA without deliberate introduction and was first detected in Maryland in 2014 and subsequently in Frederick County, VA in 2015. It has continued to expand its range in the USA and was recently detected in several eastern and western states. Despite their importance, little is known of where brown marmorated stink bug eggs, nymphs, and adults are most likely to be found in wild trees. Even less is known about where samurai wasp is likely to occur within its new range. To address these issues, traps containing a lure to attract brown marmorated stink bug were placed in the upper, middle, and lower canopy of female tree of heaven (Ailanthus altissima (Mill.) Swingle), male tree of heaven, and hackberry (Celtis occidentalis L.). Significantly more brown marmorated stink bug adults and nymphs were caught in traps near the top of trees than in those at other canopy locations, with no effect of host plant species observed. The majority of brown marmorated stink bug egg masses collected from felled tree of heaven were from the middle of the canopy. The majority of samurai wasps emerged from egg masses collected from the mid-canopy, while none emerged from those collected from the lower canopy. In a comparison of sentinel brown marmorated stink bug egg masses and yellow sticky traps placed in the upper, middle, and lower canopy of tree of heaven, the majority of samurai wasp detections occurred at mid-canopy. Both methods were found to be effective, but yellow sticky traps required less time and effort to use. This led to the development of a new sampling method for samurai wasp, in which a yellow sticky trap was deployed atop a bamboo pole in the mid-canopy of wild host trees. Using this technique, the effect of habitat type on samurai wasp captures was examined, revealing no consistent effects on detections. However, this study provided the first documentation of when samurai wasps are present and most abundant during the spring and summer. A study of host plant effects on samurai wasp captures, also using yellow sticky traps placed in the mid-canopy of trees, did not reveal consistent host plant effects on captures. These data provide important insights into the interactions of brown marmorated stink bug, samurai wasp, and their environment in the Mid-Atlantic region of the USA, as well as an efficient tool with which to study the samurai wasp.

Halyomorpha halys (Stål) (Hemiptera: Pentatomidae), an invasive agricultural pest from Asia, has established in much of the USA, where it has had significant, deleterious impacts on the production of various specialty crops. Trissolcus japonicus (Ashmead) (Hymenoptera: Scelionidae) is the predominant egg parasitoid of H. halys in Asia and considered a potential agent for classical biological control. Adventive T. japonicus populations have been detected in 15 US states since 2014 and its continued spread is anticipated, creating the impetus for developing optimized sampling methods for it that are informed by its foraging ecology. Yellow sticky cards (YSC) deployed in the lower and mid-canopy of Ailanthus altissima (Mill.) Swingle trees in Virginia captured statistically equivalent numbers of T. japonicus. Season-long monitoring of T. japonicus and H. halys over two seasons resulted in significant correlations between captures of T. japonicus and H. halys adults, second instar nymphs, and all life stages combined, revealing spatiotemporal synchrony between the parasitoid and its host. Inspection of felled pheromone-baited and non-baited A. altissima showed no effect of baiting with the H. halys aggregation pheromone on H. halys egg mass abundance. Similarly, captures of T. japonicus in pheromone-baited and non-baited trees were not significantly different. Augmenting YSC with H. halys egg masses or n-tridecane did not improve T. japonicus captures. Together, these results should improve the efficiency of T. japonicus surveillance efforts and provide important guidance for future research toward enhancing the sensitivity of sampling tools for it and the interpretation of its impacts on H. halys. / Master of Science in Life Sciences / The brown marmorated stink bug (BMSB), Halyomorpha halys (Stål) (Hemiptera: Pentatomidae), an invasive species from Asia, has become widely distributed throughout the United States as a serious pest of many important crops. Parasitic wasps that develop on eggs are often key natural enemies for reducing stink bug populations. The samurai wasp, Trissolcus japonicus (Ashmead) (Hymenoptera: Scelionidae), is the primary parasitic wasp of BMSB in Asia and is under evaluation for potential use in biological control programs. Populations of samurai wasps have been detected in the United States since 2014 without intentional introduction. Its continued spread is anticipated, creating the need for effective sampling methods to track its establishment. Yellow sticky cards (YSC) deployed in the lower and mid-canopy of tree of heaven in Virginia captured similar numbers of samurai wasps. Season-long monitoring of samurai wasps and BMSB over two seasons resulted in significant correlations between captures of samurai wasps and BMSB adults, second instar nymphs, and all life stages combined, revealing spatiotemporal overlap between the wasp and its host. Inspection of felled pheromone-baited and non-baited tree of heaven showed no effect of baiting with the BMSB aggregation pheromone on numbers of BMSB egg masses. Similarly, captures of samurai wasps in pheromone-baited and non-baited trees were not significantly different. Combining YSC with BMSB egg masses or n-tridecane did not improve samurai wasp captures. Together, these results provide important guidance for future research toward enhancing the sensitivity of sampling tools for samurai wasps and the interpretation of its impacts on BMSB.

The brown marmorated stink bug (BMSB), Halyomorpha halys (Stål) (Hemiptera: Pentatomidae), is an invasive phytophagous species native to eastern Asia. Due to its wide host plant range, it is considered among the most harmful agricultural pests in the invaded areas, including Europe, North and South America. In addition to its impact on crops, this insect causes a nuisance in urban areas, by invading buildings for overwintering using their aggregation pheromones and emitting an unpleasant smell when disturbed. The current management of this species is mainly based on the use of chemical insecticides, which show efficacy when applied frequently, with consequent negative impact on beneficial insects in the agroecosystems. As a result, there is a desire for more environmentally friendly solutions for the management of BMSB. A valid alternative is the use of exotic and coevolved biocontrol agents, for instance, the Samurai wasp, Trissolcus japonicus (Ashmead) (Hymenoptera: Scelionidae), which is already showing promising medium and long-term results against BMSB in classical biocontrol projects. Within the frame of the least-toxic alternatives, the use of the Sterile Insect Technique (SIT) in an Area-Wide management approach is potentially a valid strategy to be included in integrated control and eradication programs. The main objective of this research, therefore, was to develop a SIT for potential use in the eradication of BMSB in newly introduced areas and/or as an additional tool to reduce its impact in areas where invasive populations have been already established. However, the effective use of SIT requires producing a high number of insects, and mass rearing for such a species is considered too complicated and expensive. To overcome this limitation, we evaluated a harvest, irradiation, and release strategy using wild overwintering adults. New live traps baited with high-load pheromones have been developed for mass trapping, exploiting the natural phenomenon ruled behaviour of aggregation of BMSB in preparation for overwintering. The captures of the new pheromone traps were compared with those of identically baited sticky panels through daily services lasting 2 weeks. Following winter diapause, the collected males were irradiated with high-energy photons at four different dosages: 16, 24, 32 and 40 Gy. The effects of irradiation on the biology i.e., fertility, longevity, and mating behaviour of overwintering BMSB males were evaluated with respect to unirradiated males. To encourage the use of SIT, a linear accelerator from a hospital facility was used for irradiation instead of the classical method involving radioactive materials. A second control 0 Gy was adopted to evaluate the possible negative effects on the biology (longevity, fertility, and fecundity) of insects due to the preparation for the irradiation. Moreover, as part of an integrated pest management (IPM) strategy, the combined use of the egg parasitoid T. japonicus and SIT was considered. The suitability of sterile eggs as oviposition substrate for T. japonicus was evaluated by comparing irradiated BMSB eggs at 40 Gy, eggs obtained by fertile female mated with sterile males irradiated at 50 Gy, and refrigerated sterile eggs currently used for laboratory rearing and field monitoring. The results of the research are encouraging for SIT applications in IPM approach. 1) The new traps caught up to 15-times more adult BMSB than the sticky panels in the two weeks of collections. 2) The developed irradiation protocol that involved a 6 MV medical linear accelerator has allowed the achievement of a high level of sterility of overwintering males (over 95%) already at 32 Gy without compromising males’ longevity and mating behaviour (in no-choice conditions). No adverse effects due to the irradiation preparation protocol were observed. 3) Sterile eggs obtained by mating sterile irradiated males and fertile females (SIT eggs), showed a higher parasitoid emergence rate (%) than both those directly irradiated and refrigerated. The difference in the emergence rate is even more evident when the eggs are 20 days old, with a parasitoid emergence rate of (75.56 %) for SIT eggs compared to those irradiated (44.68 %) and refrigerated (37.57%). In conclusion: 1) the new live traps are effective in mass trapping, 2) wild harvested males of BMSB can be used in SIT, 3) the use of linear accelerators for irradiation of BMSB is a feasible alternative to classical radioactive sources and 4) sterile eggs obtained by mating sterile males and fertile females are a valid substrate for T. japonicus oviposition, supporting the potential use of SIT on BMSB.