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An adventive population of the exotic parasitoid wasp, Trissolcus japonicus(Ashmead) (Hymenoptera: Scelionidae), discovered in Michigan in 2018, is a promising biological control agent of the invasive Halyomorpha halys(Stål) (Hemiptera: Pentatomidae). Following its discovery, field releases of Tr. japonicuswere conducted over 2 yr in southern Michigan, to test how release size or release frequency impacts establishment. Sentinel eggs of H. halysand of the native Podisus maculiventris(Say) (Hemiptera: Pentatomidae) were used alongside yellow sticky cards to monitor parasitoids. In 2019 and 2020, 7,200 Tr. japonicuswere released at 16 sites. Monitoring between 2019 and 2021 yielded only 49 individuals. The captures suggest reproductive activity and overwintering success in the field but do not allow for evaluation of best release methods. Parasitism by native parasitoids was below 7%, which is similar to other states and unlikely to provide sufficient control of H. halys. The placement of sentinel eggs or sticky traps either in the lower or middle canopy of trees did not influence parasitoid capture rates. Frozen and fresh H. halyssentinel eggs were attacked at the same rate, but more native parasitoids emerged from frozen eggs. We did not find signs of nontarget effects on P. maculiventristhus parasitism rates overall were very low. These results could indicate dispersal of Tr. japonicusfrom the release sites or slow population growth. The latter may be due to the relatively low densities of H. halysin Michigan or may stem from the small founding size of our laboratory colony.

Drosophila suzukii(Matsumura) (Diptera: Drosophilidae) is a devastating global pest of berry crops and cherries. Little is understood about its biology during the winter in northern temperate regions, including potential resources that it may utilize during this period. In this study, olfactory and behavioral responses of female D. suzukiito six volatiles (methionol, acetic acid, linalool, bornyl acetate, isoamyl acetate, and geosmin) were evaluated separately for electroantennogram (EAG) and behavioral assays between summer and winter morphs. Results of EAG indicated that isoamyl acetate, acetic acid, and geosmin elicited significantly higher olfactory responses from the antennae of female summer morph D. suzukiicompared with those of female winter morph D. suzukii. Winter morph D. suzukiishowed reduced antennal response to the volatiles overall. Geosmin and bornyl acetate elicited significantly different behavioral responses from the two morphs in no-choice laboratory behavioral assays. T-maze behavioral assays with geosmin further revealed that summer morphs had a significant aversion, while winter morphs showed no significant aversion to geosmin. Overall, we demonstrate that responses of the two seasonally induced morphs to environmental stimuli are different, and future studies are justified to further understand how these physiological and behavioral differences may contribute to improved pest management of D. suzukii.

Methods for trapping spotted wing drosophila, Drosophila suzukii (Matsmura) (Diptera: Drosophilidae), have not yet been optimized for detecting this devastating pest of soft-skinned fruits. Here, we report outcomes of choice and no-choice laboratory bioassays quantifying the rates of spotted wing drosophila alightment on 5-cm-diameter sticky disks of various colors, but no fruit odors. Red, purple, and black disks captured the most spotted wing drosophila when presented against a white background. Male and female spotted wing drosophila responded identically in these tests. Significantly more D. suzukii were captured on the red and yellow disks than those presenting the corresponding grayscale for that color, proving that D. suzukii perceives colors and not just the level of target brightness. Fluorescent red is the best candidate for trap color, while clear and white are the least desirable. However, when the background was switched to black, all nonfluorescent colors were equally acceptable to spotted wing drosophila, suggesting that background must be specified when reporting spotted wing drosophila color preference. Additional spotted wing drosophila research is justified on the effects of target color against natural backgrounds.