Field evaluation of the microbial insecticide Bacillus thuringiensis serotype H-14 against floodwater mosquitoes.

Four experimental formulations of the microbial insecticide Bacillus thuringiensis var. israelensis (serotype H-14) were evaluated in the field against larvae of the floodwater mosquitoes Aedes nigromaculis and Psorophora columbiae with ground and aerial application methods. The formulations included ABG-6108D (Abbott Laboratories, North Chicago, Ill.), a wettable powder containing about 400 IU/mg, Sandoz 402-WDC (Sadoz, Inc., Homestead, Fla.), a flowable concentrate containing 600 IU/mg, and two wettable powder formulations of Bactimos (Biochem Products, Montchanin, Del.), one with 3,000 IU/mg and the other with 6,000 IU/mg. Trials against both species indicated they were similar in susceptibility to B. thuringiensis var. israelensis (serotype H-14), and that by using ground application methods, populations of second and third instars could be reduced by 83 to 100% with ABG-6108 and Sandoz 402-WDC at 0.56 to 1.12 kg/ha and with Bactimos (6,000 IU/mg) at 0.44 kg/ha. When applied aerially, approximately two to three times the ground rates had to be used to obtain similar population reductions. Fourth instars were difficult to control, requiring approximately 1.5 to 2 times the rates required for the earlier instars to obtain 80 to 100% reductions. However, these rates were not sufficient to obtain adequate control if larvae were late fourth instars.