A STUDY ON FUNCTIONAL CHARACTERS OF BACILLUS THURINGIENSIS SUBSP. ISRAELENSIS TO CHIRONOMUS KIIENSIS TOKUNAGA / 微生物学通报

ABSTRACT

Aimed at feasibility of microbiological control of Chironomidae larvae in sourcewater, Shenzhen, China, the functional characters of Bacillus thuringiensis subsp. Iaraelensis to Chironomus kiiensis tokunaga were studied for the first time. In this study, bioassays were carried out with third-instar larvae, results showed that the LC 50 s(24h) were 24.2 and 32.6 mg/L for Bacillus thuringiensis subsp. Iaraelensis IPS82 and 187 respectively. Tests in fermentation of IPS82 show good correlations between toxicity, cell density, dissolved oxygen and spore-forming phase. The tests on environmental factors influencing toxicity to Chironomus kiiensis tokunaga showed that sunlight is the most important factor, shortening the half life of Bti from 21 days in dark to 10 days; temperature variations(15～30℃) caused no impact on toxicity, but 35℃ increases 16% of larvae mortality. The toxicity of IPS82 is relatively insensitive to change pH deviated from 7 to 11, due to drop of larvae mortality from 66.7 to 40%, at pH of 3, to 16%; its toxicity is stable in low larva density (