Effect of Temperature and Humidity on the Seasonal Phenology of Drosophila suzukii (Diptera: Drosophilidae) in Wisconsin.

Drosophila suzukii (Matsumura) is an invasive pest of soft-skinned fruits that has caused significant economic damage worldwide. In this study, we focused on the seasonal abundance of D. suzukii during the early years of establishment in Wisconsin. We explored the seasonal patterns of summer and winter morphs, their reproductive output, and the effect temperature and humidity may have on their seasonal phenology. The seasonal abundance of D. suzukii during 2 yr (2014-2015) revealed that flies were detected in Wisconsin from early July to late December, with winter morphs being trapped from August through December. The adult populations trapped spanned 1 mo longer in 2015 than in 2014. The peak proportional abundance of D. suzukii in 2015 was recorded in August which was about 2 mo earlier than that in 2014. The combined factor [maximum temperature and maximum humidity] explained the most amount of variation in D. suzukii abundance consistently across the 2 yr in Wisconsin. We did not find significant differences in the fat content, number of mature eggs, proportion of females with immature eggs, or proportion of mated females between summer morph females at the beginning, summer and winter morph females during the middle, or winter morph females at the end of the collecting season in 2015. Our results build on the body of work providing a better understanding of the D. suzukii-overwintering abilities and strengthen the importance of early crop risk assessment and targeted control strategies.

Species Composition, Abundance and Seasonal Phenology of Social Wasps (Hymenoptera: Vespidae) in Wisconsin Vineyards.

Social wasps can be serious pests in fruit growing plantings and are becoming increasingly problematic for grape growers. In this study, we conducted two experiments to assess the species composition and seasonal phenology of social wasps in Wisconsin vineyards in 2015 and 2017. In 2015, three attractants were used: (1) wine; (2) heptyl butyrate (HB); and (3) acetic acid and isobutanol (AAIB) and in 2017, two attractants were used: HB and AAIB. In both years, the same eight species were trapped from the genera Vespula, Dolichovespula, and Polistes. The predominant wasp species trapped were Vespula maculifrons, Vespula vidua, Vespula flavopilosa, and Vespula germanica in 2015 and V. maculifrons, V. flavopilosa, V. germanica, and Dolichovespula maculata in 2017, in order of total abundance. The populations of V. vidua decreased in 2017 compared to 2015, indicating large inter-annual variation. In both years, AAIB lures trapped significantly more V. flavopilosa, V. maculifrons, and V. germanica, the three most prevalent species during grape harvest, than HB, whereas HB lures trapped more V. vidua than AAIB. Wine was generally attractive to all species in 2015. This study identifies for the first time the wasp species present in Wisconsin commercial vineyards using chemical attractants. This knowledge, along with the seasonal phenology of these pest species, will help facilitate the development of management strategies for social wasps in commercial vineyards.