不同温度下苏云金芽孢杆菌对金银花尺蠖幼虫的致病力

为了掌握苏云金芽孢杆菌（Bacillus thuringiensis）对金银花尺蠖（Heterolocha jinyinhuaphaga Chu）幼虫致病的最佳条件，测定了不同温度、不同浓度下的苏云金芽孢杆菌对金银花尺蠖幼虫的致死作用.结果表明，在15~35 ℃，苏云金芽孢杆菌浓度为1×10⁴，1×10⁵，1×10⁶，1×10⁷，1×10⁸，1×10⁹芽孢·mL^-1，各浓度下对金银花尺蠖幼虫均有一定的致死作用，在31 ℃时校正死亡率达到最大，分别为60.32%，67.24%，72.41%，79.31%，84.48%和91.38%，同一温度下的校正死亡率随着浓度的升高显著上升.方差分析显示，温度和浓度的交互作用对金银花尺蠖幼虫的校正死亡率没有显著影响（p>0.05）.由所建立的拟合模型计算可得各浓度对应的校正死亡率最大温度分别为29.88，31.54，32.50，31.17，33.28和32.75℃.毒性分析表明，31 ℃时苏云金芽孢杆菌的毒性最强，LC₅₀值为2.70×10³芽孢·mL^-1，高于或低于31℃，其毒性有所下降.

Pathogenicity of Bacillus thuringiensis to Heterolocha jinyinhuaphaga Chu larvae at different temperatures

To obtain the optimal pathogenicity conditions of Bacillus thuringiensis (Bt) to Heterolocha jinyinhuaphaga Chu larvae, the lethal effects of Bt on H. jinyinhuaphaga Chu larvae at different temperatures and dosages were tested in laboratory. The dosages of Bt were set as 1×10⁴, 1×10⁵, 1×10⁶, 1×10⁷, 1×10⁸, 1×10⁹ spores·mL^-1. The result showed that Bt at each dosage had a certain lethal effect on H. jinyinhuaphaga Chu larvae in the range from 15 to 35 ℃. The corrected mortality reached the highest level at 31 ℃, which was 60.32%, 67.24%, 72.41%, 79.31%, 84.48% and 91.38%, separately, and it would decrease significantly at lower or higher temperatures. At the same temperature, the corrected mortality would increase when the dosage was added. Two way ANOVA showed that the interaction of temperatures and dosages had no significant effect on the corrected mortality of H. jinyinhuaphaga Chu larvae(p>0.05). According to the established regression model, the optimum temperatures for the biggest corrected mortality at each dosage were calculated as 29.88, 31.54, 32.50, 31.17, 33.28 and 32.75 ℃, respectively. Toxicity analysis showed that the toxicity of Bt was strongest at 31 ℃, and it's LC₅₀ value was 2.70×10³ spores·mL^-1. The toxicity of Bt would decrease at the temperatures higher or lower than 31℃.