Interactions between Bacillus sphaericus and Bacillus
thuringiensis israelensis (Bti), persistence of insecticidal
activity in the mosquito habitat, and suitability of enzyme-linked
immunoabsorbent assay (ELISA) for detecting and
quantifying bacterial endotoxin in the mosquito habitat were
investigated. Interactions between the two bacterial
species were examined by laboratory and field bioassays with
larvae of Culex pipiens. In laboratory bioassays, B.
sphaericus and Bti acted independently. Antagonistic
interactions occurred with combinations of a low
concentration of one bacterium with a high concentration of
the second, however. In field bioassays, all interactions
between Bti and B. sphaericus were antagonistic. Field
bioassays with C. pipiens indicated no persistence of insecticidal activity of either Bti or B. sphaericus after
two treatments and persistence of only B. sphaericus after 3
and 4 treatments. Organic matter and high temperatures
adversely affected the accuracy of ELISA for detecting and
quantifying bacteria in the mosquito habitat and may play a
major role in detoxification of bacterial endotoxin in
nature
