苏云金杆菌对斯氏按蚊Hor株幼虫杀伤效果的分析

Killing effect of Bacillus thuringiensis israelensis on larvae of Anopheles stephensi

目的检测苏云金杆菌以色列亚种(Bti)对斯氏按蚊Hor株四龄幼虫的杀灭效果及作用特点,为合理使用Bti进行蚊虫防治提供参考标准和理论依据。方法首先采用Probit analysis生物测定的方法研究Bti剂量与斯氏按蚊幼虫累计死亡率的关系,通过线性回归分析获得相关公式,计算半致死浓度(LC50)等重要参数,探讨Bti对斯氏按蚊的杀伤效果。然后利用半致死浓度的Bti处理不同密度的斯氏按蚊幼虫,分析按蚊幼虫密度对Bti杀伤效果的影响。结果Bti对斯氏按蚊四龄幼虫的累计死亡率随作用时间和浓度的升高而增大,Bti的浓度对数值与累计死亡率P值呈较好的线性关系,根据所获得的公式计算出Bti作用12、24、48和72h后,半数致死浓度(LC50)分别为(1242±60)IU/L、(1112±45)IU/L、(1010±73)IU/L、(855±32)IU/L,95%致死浓度(LC95)分别为(4 170±138)IU/L、(3746±444)IU/L、(3462±409)IU/L、(3080±464)IU/L。而且随着幼虫密度的增加,其累计死亡率显著降低。结论 Bti株对斯氏按蚊四龄幼虫具有较好的杀伤效果,作用强、起效快,是一种较为理想的的灭蚊生物制剂;在Bti的使用剂量的确定上,应充分考虑蚊虫密度的因素,蚊虫密度越大所需Bti剂量应适当加大。

Objective To detect the killing effects of Bti on the 4th instar larvae of Anopheles stephensi and acting characteristics so as to provide primary experimental and theoretical basis for the appropriate application of Bacillus thuringiensis israelensis （Bti） in mosquito control . Methods Firstly, linear regression analysis was carried out by Probit analysis method to investigate the relationship between doses of Bti and the accumulated mortality of Anopheles stephensi larvae. And, some key parameters such as LC50 were calculated based on the obtained formula. Then, the influence of Anopheles larvae density on the killing effects of Bti was also detected by treatment with a sub-lethal dose of Bti in groups with different larvae densities. Results The accumulated mortality of the 4th instar larvae of Anopheles stephensi increased with the raises of incubation time and concentration of Bti. There was an ideal linear relationship between the logarithm of concentration of Bti and the Probit value of the accumulated mortality. According to the obtained formula, LC95 and LC95 were calculated. The LC50s at 12h, 24h, 48h and 72h post treatment were （1242±60） IU/L, （1112±45） IU/L, （1010±73） IU/L and （855±32）IU/L, respectively. The LC95s at 12h, 24h, 48h and 72h after treatment were（4170±138）IU/L, （3746±444）IU/L, （3462±409） IU/L and （3080±464）IU/L, respectively. Conclusions Bti has a strong and rapid killing effects on the 4th instar larvae of Anopheles stephensi, which indicates that Bti is a kind of ideal bio-larvicide for mosquitoes control with good killing effect. The increase of larval densities should be fully considered for choosing the doses of Bti. The dose of Bti should be increased accordingly with higher larval density.