The Study Of Insecticide Resistance And Management Countermeasure

Insecticide resistance is the major obstacle to control agriculturaland medical important pests. This worldwide problem has been documented forover 540 arthropod species. Given the tremendous difficulty and investmentassociated with the development of new, safe and effective insecticides, there isa grave need to preserve the efficacy of current and future insecticides. For thesereasons, it is essential to understand the mechanisms by which insects acquireresistance so that we can intelligently design strategies to delay its onset. Presentpaper mainly works on resistance mechanism of organophosphates (OPs) andcarbamates (CBs) in the SH-R resistant housefly, effective synergistic agent,new and safe insecticidal substances by microorganism, and constructing vectorof recombination NPV.1. AChE properties, biomolecular reaction rate constant(ki), cloning andsequencing cDNA coding AChE were carried out in the resistant(SH-R) andsusceptive(SH-S) strain of housefly. The results obtained are as follows: Thedifference in the AChE properties and ki may be attributed mainly to thedecreased affinity of OP and CB compounds for AChE from the SH-R strain.This significant decreased affinity of AChE might be due to the change in thesize or shape of the AChE from the SH-R strain. The four mutations were foundthrough comparing the cDNA sequences between SH-R and SH-R strain. Amongthem, the D422V was a novel mutation. Genes, including the AChE coding genemutation was a major resistance mechanism for the SH-R strain. Insensitivityacross different OPs and CBs is variable, because different mutations mayproduce different forms of AChE, and these provide different resistance levelagainst OPs and CBs. The study also showed that the resistance pattern of theSH-PR strain should be classified as Pattern I, which is different from the PatternII suggested by Russell et al(2004).2. It was found that iprobenfos(IBP) could synergize malathion toxicity in themalathion-resistant(RM) strain of Culex pipiens pallens Coq. The synergisticmechanism was mainly due to the inhibition of IBP on carboxylesterase(CarE)activity. The effect of mixture of IBP and malathion on evolution of malathionresistance by simulation experiment showed that, although IBP could notprevent onset of malathion resistance, could dramatically delay the evolution ofmalathion resistance. It was also found that the resistance level of Culex pipienspallens Coq was different between larva and female adults, The resistant level atthe adult stage was much higher than that of the larval stage. That is why thecontrol of mosquitoes with malathion is more effective in the larval stage than inthe adult stage. We must guard against the use of malathion in all the growthstages.3. A lot of metabolites produced by microorganism were screened for novelinsecticidal compounds, and several active metabolites were found. Twostrains of actinomyces, No.20011 and No.200578, were selected to study theiractive compounds. No.20011 strain could produce the substance with highinsecticidal activity to Aphis medicagenis and Tetranychus cinnabarinus, butlow activity to Pseudaletia separata. No.20578 strain could produce highinsecticidal active substance to Pseudaletia separata. Through isolation andpurification by solvent extraction, silic gel chromatograph, thin layerchromatograph and HPLC, the two compounds were obtained, and their puritywas 98.5% and 85.6%, respectively. The compound produced by No.20011strain was identified as piericidin A, and another compound will be furtherstudied.4. In order to increase the killing speed of NPV(nucleopolyhedroviruses) toHelicoverpa armigera(Ha), this paper carried out the work by deleting the geneof ecdysteroid UDP-glucosyltranserase(egt) and inserting the gene of aninsect-specific neurotoxin (BmK ITa1) from the Chinese scorpion Buthusmartensi Karsch in HaNPV. Two pBluescript II SK(+) vectors was generated bydeleting egt gene or inserting the BmK ITa1 gene in the egt locus. The enhancedgreen fluorescent protein (EGFP) gene was constructed as a marker in thevectors for screening the recombinants, which has be accomplished for theearly-stage research work of a new kind of recombination HaNPV.