Studying on the Insecticide Restant and Esterase Isozymes in Diamondback Moth Plutella Xylostella (L.) from Three Populations in China

In order to know the resistance level and the distribution of esterase alleles in different populations of diamondback moth from China, and to reveal the resistant mechanism at molecular level, four groups of diamondback moth were sampled for bioassay and starch gel electrophoresis. One was susceptible strain from Taiwan; other three population samples were collected from Beijing, Xuanhua Hebei province and Yunnan Yunan province, respectively. They were bioassayed at the third larval instar for tolerance to bisultap and abamectin. The data showed that: comparing with the susceptible strain, the resistant levels of three populations to abamectin were 1.21-fold, 4.51-fold and 1.25- fold, respectively. There were no significant difference in bisultap sensitivity between the field populations and susceptible strain. The results indicated that the high active Est α and Est β existed in the three populations. There are 11 different esterase isozymes in Beijing population, of them 4 Est α and 7 Est β ; 3 Est α and 5 Est β in Hebei population; 3 Est α and 3 Est β isozymes in Yunnan population. It is not likely that esterase gene polymorphism of the diamondback moth with different resistance are comes from their migration between provinces, as living larvae and eggs of the diamondback moth often found on the transported vegetables. Most probably, it comes from the transport of vegetables. Bisultap has no cross-resistance to insecticides, which are able to induce high esterase activity.