用浸叶法测定了采自我国不同地区（泰安、莱阳、南京、北京和安阳）的棉蚜品系Ⅰ、Ⅱ、Ⅲ、Ⅳ、Ⅴ对久效磷、甲胺磷、抗蚜威和灭多威等杀虫剂的抗性水平，各棉蚜品系对杀虫剂的抗性依次为Ⅴ>Ⅳ>Ⅲ，Ⅱ>Ⅰ。进一步研究表明，Ⅴ和Ⅳ品系棉蚜乙酰胆碱酯酶对杀虫剂的敏感性显著下降，Ⅱ品系次之，Ⅲ和Ⅰ品系接近于敏感品系。Ⅴ和Ⅳ品系乙酰胆碱酯酶的Km值显著下降，表明酶发生了质的变化。不同棉蚜抗性品系的酯酶（全酯酶和羧酸酯酶）活性均显著升高，其中Ⅲ品系的酯酶活力为Ⅱ品系的2倍。Ⅴ品系羧酸酯酶Km值达2460.4μmol/L，而Ⅳ品系仅为84.4μmol/L，该两个品系羧酸酯酶发生了质的变化。研究结果表明，不同抗性程度的棉蚜品系均存在代谢抗性和靶标抗性。低抗水平的棉蚜品系，以代谢抗性为主，靶标抗性为辅；中抗水平的棉蚜品系，抑或由于解毒代谢酶的活性显著增强，也可能由于靶标的敏感性显著下降；而高抗水平的棉蚜品系，依赖于代谢抗性和靶标抗性的联合作用。

ated by the PHYLIP program package inferred that AChE2 of A. gossypii is a more ancestral form of AChE. Homology modeling of structures using Torpedo californica (2ACE_) and Drosophila melanogaster (1Q09:A) native acetylcholinesterase structure as main template indicated that the two AChEs of Aphis gossypii might have different three-dimensional structures. Alternative splicing of Ace1 near the 5’-end resulting in two proteins differing by the presence or absence of a fragment of four amino acids is also reported.

A field population of the rice stem borer (Chilo suppressalis Walker) with 203.3-fold resistance to triazophos was collected. After 8-generation of continuous selection with triazophos in laboratory, resistance increased to 787.2-fold, and at the same time, the resistance to isocarbophos and methamidophos was also enhanced by 9- and 4-fold, respectively, implying some cross-resistance between triazophos and these two organophosphate insecticides. Resistance to abamectin was slightly enhanced by triazophos selection, and fipronil and methomyl decreased. Synergism experiments in vivo with TPP, PBO, and DEM were performed to gain a potential indication of roles of detoxicating enzymes in triazophos resistance. The synergism results revealed that TPP (SR, 92) and PBO (SR 63) had significant synergistic effects on triazophos in resistant rice borers. While DEM (SR 0.83) showed no effects. Assays of enzyme activity in vitro demonstrated that the resistant strain had higher activity of esterase and microsomal O-demethylase than the susceptible strain (20- and 30-fold, respectively). For glutathione S-transferase activity, no difference was found between the resistant and the susceptible strain when DCNB was used as substrate. However, 28-fold higher activity was observed in the resistant strain when CDNB was used. These results showed that esterase and microsomal-O-demethylase play some roles in the resistance. Some iso-enzyme of glutathione S-transferase may involve in the resistance to other insecticides, for this resistant strain was selected from a field population with multiple resistance background. Acetylcholinesterase as the triazophos target was also compared. The results revealed significant differences between the resistant and susceptible strain. The Vmax and Km of the enzyme in resistant strain was only 32 and 65% that in the susceptible strain, respectively. Inhibition tests in vitro showed that I50 of triazophos on AChE of the resistant strain was 2.52-fold higher. Therefore, insensitive AChE may also involved in triazophos resistance mechanism of rice stem borer.

The activity and electrophoretic mobility of nonspecific esterases, and the sensitivity of acetylcholinesterase (AChE) to organophosphate and carbamate insecticides, was determined for 21 strains or clones of Aphis gossypii of worldwide origin and related to patterns of insecticide resistance disclosed by diagnostic dose bioassays with demeton-S-methyl, pirimicarb, and permethrin. Results confirmed previous work showing the occurrence of two forms of mutant AChE, both conferring insensitivity to pirimicarb and representing the primary mechanism of resistance to this insecticide. One of these mutant AChE enzymes also caused resistance to demeton-S-methyl in its own right, whereas the other only conferred resistance in combination with moderate or high levels of nonspecific esterase activity. Lack of any correlation between permethrin resistance and quantitative or qualitative changes in esterases implied a distinct, as yet uncharacterised, mechanism of resistance to pyrethroids, possibly based on insensitivity in the target protein for these pesticides.

A field population of brown planthoppers (Nilaparvata lugens St