Bacillus thuringiensis var. israelensis (Bti) was tested as a larvicide against the mosquito, Aedes triseriatus, under laboratory and field conditions. In distilled water and exposed tire water, Bti was about 4 times more effective than it was in beech treehole water, oak treehole water, and shaded tire water, The LD-50 for Bti in the treehole water and shaded tire water was 0.4 ppm and the LD-99 was 3.0 ppm. Concentrations from 1.0 to 10.0 ppm Bti caused high mortality to mosquito larvae in all breeding habitats tested. A bioassay using laboratory-reared fourth instar Ae. triseriatus showed that under field conditions Bti loses most of its larvicidal activity in treeholes and tires within 3 to 5 days. Small scale field trials with Bti using a Hudson sprayer in a tire yard reduced Aedes triseriatus breeding by 98%.
