Bioassay methods with the silkworm, Bombyx mori for quality control of Bacillus thuringiensis formulations - Current method and its modification

Abstract

Bacillus thuringiensis has been utilized worldwide as an environmentally benign biopesticide. The quality control of formulations from B. thuringiensis are usually performed based on bioassays with insects, although the test methods and the species of test insects differ among countries. In Japan, a bioassay method with silkworm, Bombyx mori, was proposed by the Japan Plant Protection Association in 1973, which illustrated a protocol of procedure and a reference sample to calculate the relative potency of the test sample by Bombyx Unit. This bioassay method has been used without modification since that time for the quality control of all B. thuringiensis formulations commercially produced in this country. However, in order to simplify and speed up the bioassay method some modifications are called for. The authors review some problems with the current method and discuss possible modifications to resolve these issues and improve the assay.