Management of Japanese Beetles with Biorational Insecticides
Japanese beetles are an invasive species in the United States that feed on the roots of plants, leaves, and flowers. Every year, the US spends upwards of $616 million to manage Japanese beetles and replace damaged turf and ornamental plants. Current management techniques are ineffective at controlling the populations or have non-target effects on the environment and beneficial insects. Two entomopathogenic biorationals, Beauveria bassiana and Bacillus thuringiensis galleriae (BTG), have shown promising effects in reducing Japanese beetle numbers. However, no previous studies have used both biorationals at the same time. Over 2,000 Japanese beetle adults were subject to different combinations of Beauevria bassiana and BTG to examine the relationship between the two biorational insecticides. Petri dishes were set up with filter paper, linden tree leaves, and 10 beetles per dish and were then sprayed with a solution of BTG, B. bassiana, or a combination of the two. Mortality was counted every 24 hours for four days. The results of the singular bioassays gave a lethal concentration 50 value of 1.05 mg/mL for BTG and 0.83 mg/mL for B. bassiana. The results of the interaction bioassay showed no added benefits of combining the two products. B. bassiana had the highest mortality and the addition of BTG added no statistically significant differences. Overall, combining BTG and B. bassiana did not increase the effectiveness of managing Japanese beetles compared to using the biorational insecticides alone.