EFFECTS OF METHOPRENE AND BTI (BACILLUS-THURINGIENSIS VAR ISRAELENSIS) ON NONTARGET INSECTS

The effects of mosquito larvicides Bacillus thuringiensis israelensis (Bti) and methoprene, on non-target benthic invertebrates were studied in a divided pond experiment in south-central Minnesota, USA, during the spring and summer of 1989. Density and biomass of insects and othe r benthic macroinvertebrates were quite low in all sections of the thr ee ponds studied, which may have been due to three consecutive years o f drought, but richness appeared to be high and we observed no evidenc e of dominance by a particular group. We also saw no evidence of negat ive effects of larvicide treatment on density or biomass of any invert ebrate group, nor was there a treatment-related decrease in richness o f benthic invertebrate taxa under these drought conditions.