The toxicity of the insecticides and the mechanism associated with deltamethrin resistance in melon thrips ( Thrips palmi Karny ) collected from Kaohsiung and Pingtung area

• Main Authors: Ping-Tsung Tsai, 蔡秉宗
• Other Authors: Chu-Ying Hsin
• Format: Others
• Language: zh-TW
• Online Access: http://ndltd.ncl.edu.tw/handle/38982093099531735067

碩士 === 國立屏東科技大學 === 植物保護系所 === 97 === Thrips palmi Karny was the major pest on eggplant and melon in central and southern Taiwan. Farmers mainly used pesticide to control T. palmi. The susceptibility of T. palmi to three insecticides, especially pyrethroids, decreased obviously under continuous selection pressure of insecticides. This study was to test the toxicity of imidacloprid, formetanate and deltamethrin, using leaf dip method, to the second-instar larvae of T. palmi that were obtained from the mass rearing of T. palmi collected from eggplants fields with different pesticide application history. The best efficacy of insecticides was imidacloprid, followed by formetanate and deltamethrin. Using T. palmi from Tai-Wu area as reference strain, the resistance ratios of technical and commercial grade of deltamethrin to T. palmi collected from Guai-Lai area were 7.7 and 17.5 times respectively. The deltamethrin resistance of T. palmi collected form Chi-Shan area increased 7.4 and 16.3 times within 10 months. These results implide T. palmi from Guai-Lai and Chi-Shan developed deltamethrin resistance. The synergistic ratio of deltamethrin with piperonyl butoxide was over 21.77 and 18.71 found in the T. palmi collected from Guai-Lai and Hai-Fong area. These results suggested that the increased toxicity of cytochrome P450 was involved in the deltamethrin resistance of T. palmi. The total RNA of T. palmi from Tai-Wu, Hai-Fong and Guai-Lai area was reverse-stranscripted to cDNA. These cDNA were amplified by polymerase chain reaction ( PCR ) using CYP6 degenerate primers. A single band of 390 bp was obtained in the electrophorogran in every aduts and larvae of T. palmi from all three areas. This band, named as CYP6-TP, was confirmed as a member of CYP6 family after sequencing. The specific primers for CYP6-TP gene was designed and the real-time PCR using cDNA of T. palmi from Tai-Wu, Hai-Fong and Guai-Lai as template was conducted. The amount of CYP6-TP gene expression in T. palmi from Guai-Lai and Hai-Fong showed 4.63 and 2.81 times than that from Tai-Wu area. These results of gene expression were positively correlated with the resistant ratio data in bioassay. Therefore, the thrips from Guai-Lai and Hai-Fong area developed deltamethrin resistance that was related to the increased expression of CYP6-TP gene.