Application Research Of Bacillus Thuringiensis Subsp. Israelensis On Mosquito Larvae Control

Some species of mosquitoes are vectors of diseases such as malaria and yellow fever. People ever used mineral, plant powder and chemical pesticide to control the mosquitoes. Now Bacillus thuringiensis subsp. Israelensis(Bti) is highlighted as a kind of new biological pesticide which could control the mosquito larvae without bad effect to pest natural enemies, human, livestock, beneficial organisms. And it is environmental friendly.Aimed at feasibility of microbiological control of mosquito larvae in Africa,, we compared the toxicity of Bti IPS82 and KN-11 to Culex fatigans larvae through bioassay with third instar larvae. We also studied the fermentation characters of Bti IPS82 and the effect of environmental factors to the toxicity of this standard strain.The results of bioassay showed Bti has high toxicity to Culex fatigans larvae. The LC₅₀ (24h) of Bti IPS82 and KN-11 to Culex fatigans larvae are respectively 23.7mg/L and 33.6mg/L. Tests in fermentation of IPS82 showed good correlations between toxicity, cell density, dissolved oxygen and spore forming phase, and we could get the highest toxicity(LC₅₀ 24.2 mg/L) when it was fermented for 36h in lab. The tests on environmental factors including sunlight, temperature variations, pH and host density influencing toxicity to Culex fatigans larvae 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°C) caused no impact on toxicity , but 35°C increases...