Toxicity of 11 representative pesticides through different modes of pollution transmission to silkworm（Bombyx mori）

【Objective】This study aimed to clarify the internal absorption and transmission properties of 11 representative pesticides on mulberry trees and their toxicity to silkworm(Bombyx mori) by fumigation and contact, so as to provide scientific basis for effective prevention and control of pesticide poisoning in silkworm rearing. 【Method】Mulberry trees were treated with 11 representative pesticide preparations which belonged to six categories of pesticides that used silkworm as a marker, on the 3^rd, 30^th and 120^th d after treatment, mulberry leaves were collected and fed to the 3^rd and 5^th instar larvae of silkworms respectively. The poisoning symptoms of silkworm were observed, and the pollution transmission modes of various pesticides on mulberry trees were judged and analyzed. At the same time, the toxicity of all kinds of pesticides to silkworm was judged comprehensively by directly treating silkworm with fumigation and contact. 【Result】The symptoms of silkworm poisoning caused by different pesticides showed many similar characteristics, such as refusing to eat, vomiting, contraction, curling in c-shape or s-shape, shortening of body length, etc. Mulberry leaves on the 3^rd and 30^th day after root irrigation with different pesticides could cause silkworm poisoning, which showed that all the 11 pesticides could absorb and transmit up through mulberry roots, in addition, seven pesticides, namely dimehypo, thiosultap monosodium, cypermethrin, thiamethoxam, imidacloprid, pyripropyl ether, chlorine benzamide, were still highly toxic in the fresh mulberry leaves after cutting. Mulberry leaves on the 3^rd day after spraying of 11 kinds of pesticides could cause poisoning symptoms of silkworms. At the 30^th day after spraying, except for trichlorfon and dichlorvos, the mulberry leaves sprayed by 9 other pesticides could also cause the poisoning symptoms of silkworm. At the 120^th day after spraying, only the mulberry leaves sprayed with chlorine benzamide and avermectin could cause silkworm poisoning, that was, the harmful components of these two pesticides had bidirectional transmission characteristics to mulberry. The toxicity of the 11 pesticides to the silkworm was greatly different, and the order of toxicity was dichlorvos>cypermethrin=bifenthrin>thiamethoxam>imidacloprid>trichlorfon>dimehypo>thiosultap monosodium>avermectin>chlorine benzamide>pyripropyl ether. 【Conclusion】The 11 pesticides have all both internal absorption and upward transmission to the roots and leaves of mulberry, and the chlorine benzamide and avermectin have bidirectional conduction to mulberry. There are significant differences in the toxicity of different pesticides to the silkworm, but the toxicity of pyripropyl ether, chlorine benzamide and avermectin were weaker. The results show that the 11 pesticides had different conduction efficiency in 3transmission modes(irrigation root, leaf spray, fumigation and contact killing), and each has its own dominant conduction mode.