Pesticide Toxicology Laboratory

Bti was applied to experimental ponds at 2 kg/ha, 4 kg/ha, and 10 kg/ha; which resulted in a 23-61%, 52-72%, and 53-88% reduction of Chironomini and Tanytarsini larvae, respectively, during a four week post-treatment period. In a golf course pond, a 3 kg/ha Bti treatment resulted in a 27-65% reduction of total Chironomidae larvae fourteen days after treatment. In both exposure systems, effects on members of the Chironomidae family were short-lived due to reinfestation from untreated areas. Bti had no significant effect on rotifers, Cyclops spp., Daphnia spp., ostracods, the mayfly nymph Baetis sp., corixid and notonectid adults, and larvae and adults of hydroporine and hydrophilid beetles at any treatment level.