Study On Resistance Monitoring, Resistance Selection To Diafenthiuron And Resistance Biochemical Mechanism Of Diamondback Moth(Plutella Xylostella)

Diamondback moth, Plutella xylostella (L.), is one of major pest of crucifer vegetables, and makes deep influence to the products and quality of crucifer plants in the world. Traditional control diamondback moth mainly relies on the use of insecticide, but the development of diamondback moth resistance to insecticides quickly, causing control difficulties. It is more and more difficult to develop new pesticides. The diamondback moth resistance monitoring and resistance mechanism is studied.Four field populations of Plutella xylostella L. were collected from Yichang and Wuxue of Hubei province, Yueyang of Hunan province and Luoyang of Henan province, respectively, the toxicity of five insecticides to the four populations were done by leaf dipping method. The results showed that from 2008-2009 the populations of luoyang, wuxue, yichang and yueyang to chlorfluazuon produced middle or high levels of resistance respectively, the resistance ratios were 24.80 to 126.85,32.27 to 95.11,42.68 to 135.06 and 26.58 to 85.06. The five field populations produced low to medium level resistance with cartap between 6.67-26.45-fold resistances. For spinosad resistance in between 3.41-11.59-fold, resistance from the low to middle level resistance sensitivity; diafenthiuron and chlorfenapyr were still in the sensitivity.Through selection for resistance to diafenthiuron, the resistance of diamondback moth to the insecticide increased 22.40-folds after 17 generations compared with relatives susceptible colony. Meanwhile, estimation of realized heritability (h2) of resistance was studied based on the Tabashnik's method, and estimated the development of resistance rate. The results suggested that the realized heritability (h2) was 0.0750 for F0-F20. it required 19.57-43.22 generations for diafenthiuron to obtain 10-fold increase in LD50 under selective pressure of 50%-90%mortality for each selective generation.Study on the cross-resistance of diafenthiuron to several insecticide in diamondback moth, and the activity of monooxygenases, glutathione-s-transferases(GSTs) and carboxyl esterase(CarE) between the different strains was done. The results showed that the strain of P. xylostella with resistance to diafenthiuron did not show any cross-resistance to spinosad and bete-cypermethrin, the resistance ratios (RR) were 0.33 and 0.85 respectively compared with that of unselected strain. The low level cross-resistance was demonstrated to chlorfenapyr and the resistance ratio (RR) was 4.66. Biochemical analysis was conducted to compare the 3 kinds of enzyme activities of two different strains, which were resistance of diafenthiuron strain and relatively susceptible colony. Between the two strains, the activities of glutathione-transferees (GSTs) and MFO were highly remarkable different, the ratio of enzyme activities of two strains were 1.57 and 2.22, respectively. Whereas the activity of carboxylesterase(CarE) was not remarkable different. The result indicated that glutathione-transferees (GSTs) and MFO might be involved in resistance mechanism of Diamondback moth to diafenthiuron, Whereas the CarE was not related.