Bacillus thuringiensis var. israelensis (Bti) is a biopesticide that has seen increased use in the United States as a safer alternative to chemical pesticides. Bti is considered to be relatively target specific in control effects largely limited to Dipterans in the suborder Nematocera, such as mosquitos (Culicidae), black flies (Simuliidae), and non-biting midge flies (Chironomidae). However, an increasing number of studies, primarily in the Rhone River Delta and the Rhine River, indicate significant food web consequences to non-target organisms (NTOs). A Bti sprayed system and an unsprayed system were sampled over the course of five months to observe potential non-target effects on Odonata. At each system, two approximately 100-meter transects were walked for visual observation of adult Odonata and one transect each month was sampled for benthic macroinvertebrates. A total of 81 and 278 adult Odonata were observed along the sprayed and unsprayed systems, respectively, while 1,114 and 1,089 aquatic specimens were sampled from the sprayed and unsprayed sites. The differences in adult Odonata observations across the systems were not statistically significant using a two-sample t-test (p = 0.194). However, it is likely that the result occurred due to the dataset being too small. It is recommended that future studies incorporate a larger sample size to better show if an effect is present.
Ian Emanuel (Wed,) studied this question.