Effects of Rain and Insecticides on Drosophila Suzukii Abundance and Behavior
Spink, Katherine Rose
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An invasive insect to the Unites States, Drosophilia suzukii (SWD) has been destroying marketable fruit since its introduction, particularly blueberries. The current pest management strategy relies heavily on insecticide sprays to protect fruit from infestation. Though research has been done on the efficacy of different insecticides against SWD, only one previous study has looked at the impact of rain on insecticide efficacy against SWD. This study’s aim was to determine if there was an effect of rain on fly behavior, effect of rain on insecticide effectiveness, or if there was an effect of rain duration on insecticide effectiveness. We hypothesized that rain would cause a change in SWD behavior, and that rain and rain duration would decrease insecticide effectiveness, causing an increase in SWD abundance. We performed this experiment by applying insecticides and simulating rainfall using the irrigation system in two different blueberry varieties, while collecting in-field observational data. This study found no significant effect of rain on fly behavior. There was a significant decrease in fly populations in insecticide sprayed rows compared to unsprayed rows, but no significant differences in fly population numbers between rain and no rain treatments. We hypothesize that this may be due to the immediate fatal impact of insecticide sprays on in-field fly populations, leaving no time for recolonizations from surrounding areas. If so, this would strengthen the case for the use of border rows in fields, as they would act as strong deterrent for neighboring flies trying to infiltrate the fields, allowing for continued protection of the field and fruit after a rain event.