Bioassay to assess the toxicity of bacillus thuringiensis to daikon leaf beetle (Coleoptera: chrysomelidae)

We developed a new method to rear daikon leaf beetles, Phaedon brassicae Baly (Coleoptera: Chrysomelidae), on a diet of Cruciferae leaves in a growth chamber. Eggs were stored at 4 degrees C for 30 days without significant loss of viability. A bioassay using artificial diet was developed to standardize the assessment of toxicity of a powdered crystal-spore preparation of Bacillus thuringiensis strain YBT-0618 to P. brassicae larvae. When the diet containing this powder preparation was stored at 4 degrees C for a period of 7 days, the coefficient of variation of the median lethal concentration (LC(50)) values in three replicates was 0.060. The reproducibility, or precision, of the bioassay results was optimal when, at each dilution, 30 neonates were exposed and incubated for 72 h at 25 degrees C, 65-75% RH, and a photoperiod of 12:12 (L:D). Copyright 1999 Academic Press.