Resistance Monitoring On Plutella Xylostella In Central China And Resistance Mechanism Of Plutella Xylostella

Diamondback moth (DBM) Plutella xylostella is one of the most destructive pests of crucifers, could loss yield and influence quality. Chemical control is the most effective method to control DBM, but unfortunately, it had developed and increased resistance to various insecticides, as a result, it had become one of the most difficult pests to manage in the past50-year around the world. In this paper we monitored resistance of field populations to common insecticides in central China, screened synergists to diafenthiuron to control DBM, studied sublethal effects of diafenthiuron on DBM, studied effects and inhibitions of diafenthiuron on ATPase.1Resistance monitoring of field populations in central China to common insecticidesThis study determinated susceptibilities of field populations in central China (Yueyang, Luoyang, Yichang, Wuxue, Yunmeng) to common insecticides by leaf-dipping method, results indicated that resistant levels were various. Resistances of DBM to abamectin increased from moderate to high resistant level. Resistances of DBM to Bt and beta-cypermethrin decreased in some extend, but still in high or extreme high resistant level. Resistances of DBM to chlorfluazuron ranged from moderate to high resistant level, while resistance to chlorantraniliprole, indoxcarb and spinosad ranged from low to moderate resistant level, and resistance showed increasing trend. DBM to chlorfenapyr, diafenthiuron, tebufenozide, cartap showed low-level resistance. In field, farmers should pay high attention to application of biopesticides, such as abamectin, emamectin benzoate, Bt, et al.2Synergism of3synergists with diafenthiuron against DBMTo reduce the dosage of active ingredient, and raise use efficiency of diafenthiuron, toxicity ratio and synergistic ratio of synergists (DEM, TPP and PBO) with diafenthiuron were determinated by leaf-dipping method. The results showed that DEM, TPP and PBO could raise toxicity ratio and synergistic ratio of diafenthiuron against DBM. While ratios of DEM, TPP and PBO with diafenthiuron were1:5,1:5,1:3, toxicity ratios were1.86, 2.29and2.43, respectively. Synergisms of DEM, TPP and PBO with diafenthiuron increased to different extent, with synergistic ratios were1.41,1.36and1.42, respectively.3Sublethal effects of diafenthiuron on DBMResults showed that sublethal dosages of diafenthiuron influenced development and fecundity of DBM (parental generation, first filial generation). With concentrations of diafenthiuron increasing, pupation period and pupal duration of parental generation prolonged, while pupation rate, emergence rate and oviposition quantity of parental generation decreased; hatching rates of parental generation were all greater than90%; both pupal weight of male and that of female of parental generation showed no significant difference at p=0.05. Pupal duration of first filial generation prolonged with increasing of concentrations of diafenthiuron, while pupation rate, emergence rate and oviposition quantity decreased; pupal weight of female first filial generation showed no significant difference, but pupal weight of male showed significant difference at p=0.05.4Effects and inhibitions of diafenthiuron on activities of Na-K-ATPase, Ca-ATPase and Ca-Mg-ATPase in DBMResults showed that activities of Na-K-ATPase and Ca-Mg-ATPase of resistant strain (R-) were greater than that of susceptible strain (S-), but activity of Ca-ATPase of R-strain was less than that of S-strain, indicated that activities of Na-K-ATPase and Ca-Mg-ATPase of R-strain were inhibited. Diafenthiuron significantly inhibited activities of Na-K-ATPase, Ca-ATPase and Ca-Mg-ATPase, and inhibition ratios increased while concentrations of diafenthiuron increased, inhibition ratios of diafenthiuron to S-strain were greater than that of R-strain. Inhibition ratios were the highest under treatment of100mg/L diafenthiuron, inhibition ratios of Na-K-ATPase in S-, R-strains were40.10%,28.62%, respectively, inhibition ratios of Ca-ATPase in S-, R-strains were47.87%,27.55%, inhibition ratios of Ca-Mg-ATPase in S-, R-strains were39.32%、36.36%, respectively.