Study On Pesticide Resistance Of Spodoptera Exigua (H(?)bner) (Lepidoptera: Noctuidae)

Beet armyworm, Spodoptera exigua (Lepidoptera:Noctuidae), is widely distributed in the world. It is a polyphagous and gluttonous pest of 170 species of host plants. The damage, which was occurrent previously, has become gradually serious in some areas of the country since 1990, so has its resistance problem as a result of slathering insecticides.In recent years, Spodoptera exigua has arised very grievously in Chongqing, impacting qualities and quantities of vegetables seriously. The article researched and discussed resistance situation, selection of effective insecticides and resistant mechanism of Spodoptera exigua, in order to offer theoretical grounds of resistance management of the pest The project was supported by Chongqing Science Committee (6606), and after 3 years' study, the main results are as follows.1. Resistance monitoring of Spodoptera exigua in six areas of ChongqingResistance of Spodoptera exigua to phoxim, beta-cypermethrin and methomyl was tested by topical application in Dadukou, Jiulongpo, Fengdu, Fuling, Changshou, Yunyang.The results indicated that Spodoptera exigua in Chongqing had developed moderate levels of resistance to the three insecticides mentioned above, to phoxim with 7.90-28.05 folds, to beta-cypermethrin with 13.50~3l.50 folds, to methomyl with 19.86-30.76 folds.Resistance monitoring to six insecticides showed that Spodoptera exigua in the shallot field of Dadukou district had developed resistance to many kinds of insecticides, moderate levels of resistance to phoxim with 28.05 folds, to beta-cypermethrin with 28.90 folds, to methomyl with 30.76 folds, to tebufenozide with 11.78 folds, and high levels of resistance to chlorpyrifos with 47.69 folds; but susceptible to chlorfuazuron( 1.16 folds).Resistance level was consistant with the level of insecticide application. The levels of insecticide application are high in two important vegetable bases of Dadukou and Jiulongpo, which led to high resistance levels. The level of insecticide application was lower in Yunyang which is remote, so is the resistance level.2. Toxicity of 11 insecticides to the 3rd-instar larvae of Spodoptera exigua and field testToxicity of 11 insecticides to the 3r -instar larvae of Spodoptera exigua was tested by dipping method. The results showed that the decreasing order of relative toxicity of 11 insecticides was arranged as follows: metlyl-amineavermetin,spinosad,chlorfuazuron,methoxyfenozide , azadirachtin,abamectin,aiphacypermethrin,tebufenozide,chlorfenapyr,beta-cypermethrin, phoxim.Field test of 5 insecticides to Spodoptera exigua was carried out in the shallot field. Theresults showed that metlyl-amineavermetin and spinosad had good and quick control effects of 77.04% and 70.56% after 1 day, 65.70% and 65.08% after 3 days, 64.02% and 63.07% after 7 days, respectively.Insecticides such as metlyl-amineavermetin ,spinosad ,chlorfuazuron,methoxyfenozide, with high effect and low toxicity, were suggested to be popularized in vegetables.3. Difference in insecticide tolerance and enzyme activity of Spodoptera exigua larvae at different instarsThe toxicity of phoxim, aiphacypermethrin, methoxyfenozide, chlorfluazuron to different instar larvae of Spodoptera exigua was tested using the dipping method. Insecticide tolerance of the larvae at the 2nd, 3rdand 4th instar stages increased with their development, being lowest in the 2nd instar larvae and rising sharply at and after the 3rd instar stage. Mg protein being unit, the activities of Ache, ALP> CarE, GST decreased with larvae development. Per insect being unit, the activities of drone enzyme and detoxifying enzyme increased sharply with larvae development.4. Synergism of synergists to insecticides and inhibiting effect principles of synergists to enzymesSynergism of three synergists(PBO, DEM, TPP) to phoxim, Aiphacypermethrin and chlorfenapyr was tested by dipping method. The result showed that it had high Synergism of DEM to phoxim and high Synergism of PBO to aiphacypermethrin and chlorfenapyr. The resistance to phoxim was mainly associated with GST. The resistance to aiphacypermethrin and chlorfenapyr was mainly associated with MFO.Inhibiting effect principles of synergists(PBO, DEM, TPP) to microsomal O-demethylase, GST and CarE was studied. The result showed that the dose of synergists was parallel to inhibition rate of enzymes in a certain range. Beyond the certain range, inhibition rate no more increased and even decreased with dose increasing.The research indicated that the same synergist had different synergism to different insecticides. And different synergist had different synergism to the same insecticide. Blending rate between synergist and insecticide effected synergism.5. Effect of different diets on the susceptibility to insecticides and enzyme activity of Spodoptera exiguaSingle dose-mortality rate of aiphacypermethrin and chlorfenapyr to the 3rd-instar larvae of Spodoptera exigua fed on artificial diet, pakchoi, shallot, cowpeas and water spinach was tested by...