A modified bioassay for microbial mosquito larvicides.

The proposed bioassay-the grid assay-eliminates the influence of cannibalism while allowing recycling to take place. The LC50 values of the grid assay were intermediate to those of the group and the individual assay. The grid assay thus reflects the true toxicity values of the microbial pesticides being tested. Viable count studies of the microbial pesticides employed, viz., Bacillus thuringiensis H-14 and Bacillus sphaericus 2362, performed along with the assay support the results of the bioassay.