Evaluating Host Plant use by Spotted Wing Drosophila, Drosophila suzukii, in Minnesota.

Abstract

Spotted wing drosophila, Drosophila suzukii Matsumura (Diptera: Drosophilidae), is newly established in North America and become one of the most devastating pests for small fruit crops. With a broad host range, thin-skinned berries are particularly susceptible to infestation, and fruit producers are desperate for methods to control this pest. One of the keys to developing an integrated management program for SWD is to understand host preference, varietal susceptibility of crop hosts, and overall susceptibility and use of non-crop hosts. In this thesis, the infestations levels and host plant growth stages were recorded over time during growing seasons of one day in 2014, and various sampling dates in 2015 and 2016 in Minnesota. Both crop and non-crop host plants were examined for their phenological and overall susceptibility. The first research chapter was performed working in replicated small plots, experiments were conducted to evaluate differences in varietal susceptibility on cold hardy red primocane fruiting raspberries. Significant differences were observed in both the level of infestation and in the average number of larvae per berry by variety. In addition, it appears that there is a significant negative correlation between the level of infestation and the number of larvae per fruit with the time of sampling, but only an interaction of variety and time for the number of larvae per berry. The second research chapter was performed using nine field sites of either farm or non-farm wild locations separated by a minimum of 400 meters. Crop hosts: raspberry, blueberry, and elderberry, as well as non-crop host plants were examined and sampled for fruit ripening stages an infestation rates. Significant differences were observed in infestations within non-crop host plants and crop host plants. Crop hosts sustained infestations starting in the green phenological stage. These data provide a better understanding of the biology and ecology of this pest which is critical in refining current management practices. Knowledge of these interactions can aid in optimizing control strategies such as fine-tuning spatial and temporal control measures, which may be particularly important for early season infestations.