Studies On The Insecticide Resistance In Striped Flea Beetle Phyllotreta Striolata (F.)

Compared with its insectarium population reaed under free insecticide condition , the field resistant populations of phyllotreta striolata, which were collected from Hontang (Ht) and Jianxin (Jnx) in Fuzhou and Jingxi ( Jgx) in Minhou respectively , displayed that the resistance ratios were 1.8-2.6 fold to phoxira,6.7-14.2 fold to methamidophos,1.6-5.0 fold to diclhorvos,8.4-27.0 fold to chlorpyrifos,6.5-16.4 fold to aphate, 1.7-4.6 fold to methomy 1,2.6-3.7 fold to carbosulfan, 12.4-17.4 fold to fenvalerate,5.6-6.2 fold to cypermethrin,3.6-8.2 fold to Beta-cypermethrin,5.1 -17.2 fold tolamboda-cyhalothrin,4.3-10.2 fold to deltamethrin, 2.0-4.0 fold to fipronil ,respectively . Avermectins , chlorfluarzuon, Bacillus thuringiensis and imidacloprid showed low toxicity under the conventional control dose .Great seasonal variations of insecticide resistance to methamidophos , dichlorvos , methymol , fenvalerate , cypermethrin , fipronil , and avermectins were found by field monitoring in p. striolata in the population of Jnx . The levels of insecticide resistance showed that spring and autumn were among the.highest among one year, summer lower than that of spring and autumn ,and winter was the lowest of one year.The flunctuations of avermectins resistance were the lowest among the insecticides resistance .Cotoxicity test showed that, the mixtures of dichlorvos with fenvalerate or cypermethrin , and methamidophos with fenvalerate or cypermethrin ,and methymol with fenvalerate or cypermethrin ,and carbosulfan with fenvalerate or cypermethrin ,and fipronil with fenvalerate or cypermethrin exhibit remarkable synergism.of which the cotoxicity coefficient (CTC) were 404.7,490.5,190.5,199.2,398.0,647.0,359.4,1065.9,219.2 and 336.8 respectively.However , no obvious synergisms were found by the mixtures of phoxim with fenvalerate or cypermethrin and chlorpyrifos with fenvalerate or cypermethrin, of which the CTC were 88.6,99.5,107.2 and 103.1 respectively.There existed the different extent synergistic effects on the susceptibility to methamidophos, diclhorvos, methymol,fenvalerate, cypermethrin, fipronil,avermectins by the synergists PB , TPP and DEM in the Jnx population of p. striolata. The facts suggested that a multiple resistance mechanism was exsisted in the Jnx population of p. striolata, the resistance mechanismswere mainly associated with the increasing activities of carbolic acid esterase ( CarE) , mixed-function oxidases ( MFO) and glutathione- S- transferase ( GSTs).