Abstract
A silkworm assay using the 3rd instar stage of silkworm, Bombyx mori and a diet incorporation method has been utilized for the quality control of Bacillus thuringiensis (Bt) products in Japan since 1973. The potency of test sample relative to a standard was calculated based on lethal activity (LC50). The LC50 values were usually estimated by probit analysis on the mortality at the levels of 5–6 doses. In the present study the author tried simpler silkworm assays based on the lethal activity of Bt products against the 2nd instar of silkworms using 1–2 doses. It was shown that the potency of the sample relative to the standard based on assays with 1–2 concentrations is similar to that based on assays with six concentrations.
