苏云金杆菌与高效氯氰菊酯对美国白蛾的协同作用

Synergism of β-cypermethrin and Bacillus thuringiensis against Hyphantria cunea

为了明确苏云金杆菌Bacillus thuringiensis(Bt)和高效氯氰菊酯的协同作用,采用Bt预处理及直接混用2种方式施药,室内饲毒法测定了2种药剂对美国白蛾Hyphantria cunea(Drury)2龄幼虫的活性,同时研究了高效氯氰菊酯对Bt生长曲线的影响。结果表明:试虫先用每mL含1×106个孢子的Bt S19菌悬液预处理,1 d后再用系列浓度的高效氯氰菊酯处理,其48 h的LC50值为0.76 mg/L,而未经预处理,仅用高效氯氰菊酯处理48 h的LC50值为1.28 mg/L;2种处理在高效氯氰菊酯质量浓度为2.25 mg/L时对试虫的半致死时间(LT50值)分别为9.2 h和34.7 h,两者间增效作用明显。对于直接混用,采用1×106个/mL的Bt S19与6 mg/L的高效氯氰菊酯混剂处理,增效作用明显,72 h的共毒系数为122.5,此后再增加高效氯氰菊酯的浓度则表现出轻微的拮抗作用。高效氯氰菊酯处理可使Bt生长对数期延迟,且浓度越高影响越大,说明高效氯氰菊酯可影响Bt芽孢萌发,使菌体增殖延迟。研究表明,先用Bt预处理后再使用高效氯氰菊酯对美国白蛾的作用效果优于二者直接混用。

The synergetic effect of β-cypermethrin and Bacillus thuringiensis（Bt） was studied by bioassay through Bt pre-treatment before β-cypermethrin application or mixing together with β-cypermethrin in the lab.At the same time,the effect of β-cypermethrin on the growth-curve of Bt was determined.The results showed that the LC50 values of β-cypermethrin against 2nd larvae of Hacillus cunea,pre-treated by Bt S19 at 1×106cell/mL one day before the treatment of β-cypermethrin or not,were 0.76 and 1.28 mg/L in 48 h respectively.And the LT50 values of the two treatments were 9.23 h and 30.67 h,respectively,when the concentration of β-cypermethrin was 2.25 mg/L.These results demonstrated that there were synergized action between Bt and β-cypermethrin by Bt pre-treatment.When β-cypermethrin mixed together with Bt,the co-toxicity coefficient（CTC） was 122.5 as the concentration of β-cypermethrin and Bt S19 was 6 mg/L and 1×106cell/mL respectively.However,the mixture showed some antagonism as the concentration of β-cypermethrin increased.The growth-curve experiment of Bt revealed that β-cypermethrin delayed the exponential phases of Bt,and the effect related with the concentration of β-cypermethrin positively,which suggested that β-cypermethrin might affect the germination and growth of Bt.All these experiments indicated that Bt pre-treatment before β-cypermethrin application was more efficiency than the mixture of β-cypermethrin and Bt against H.cunea.