苏云金杆菌与灭幼脲混剂对美国白蛾幼虫 围食膜的破坏研究

为明确苏云金杆菌(Bt)与灭幼脲混剂对美国白蛾幼虫的毒杀效果,笔者对美国白蛾4龄幼虫围食膜被破坏的状况进行了研究。经超薄切片透射电镜观察发现,美国白蛾4龄幼虫围食膜表面平整光滑,有较明显的多层结构。经Bt+灭幼脲混剂对美国白蛾4龄幼虫处理120 h后, 围食膜上出现较多的白色和黑色斑点状孔洞,并扩大为斑块状孔洞,形成了薄而易脆、易断或溃烂、无弹性的围食膜碎片,并致围食膜被破坏和幼虫死亡。试验证明,Bt+灭幼脲混剂对白蛾4龄幼虫围食膜的破坏最快,Bt和灭幼脲单剂次之。同时,经Bt+灭幼脲混剂及其单剂对美国白蛾4龄幼虫的林间LT₅₀、LT₁₀₀值和飞防毒杀速率测定发现,Bt+灭幼脲混剂对美国白蛾幼虫的致死率均高于其单剂,毒杀速率快于单剂。因此,Bt+灭幼脲混剂处理可较快地破坏白蛾4龄幼虫围食膜,其毒杀速率明显提高。

Destruction of the peritrophic membrane of the larvae of Hyphantria cunea Drury by the mixture of Bt and Chlorbenzuron

The ultrathin section was studied by the observation of electron microscope. The results showed that the peritrophic membrane(PM)presented a more obvious multilayer structure, and the surface was evenness and smooth in the 4^th instar larvae of Hyphantria cunea Drury. After treated 120h by using the mixture of Bt and Chlorbenzuron on larvae of H. cunea Drury, many white and black spots were formed on PM. Then the spots expanded to patchy pores. Finally thin and brittle, easily broken or fester, inelastic PM fragments were formed. It lead to destruction of the PM and death of larval. The test proved that the damage effect of the treatment of the mixture of Bt and Chlorbenzuron on the PM of the 4 instar larvae of H. cunea was the fastest, and which of the single agent of Bt and Chlorbenzuron on the PM was the second. At the same time, the tests of the value of LT₅₀, LT₁₀₀ of the 4^th instar larvae of H. cunea and the air-spraying control effect by using the mixture of Bt & Chlorbenzuron and its single dose proved that the mortality rate of the mixture was higher than that of the single dose, and the rate of death toxicity of the mixture was faster than single agent. The results showed that the mixture could quickly destroy the PM of the 4^th instar larvae of H. cunea, and the toxic effect of the treatment was significantly enhanced.