INSECTICIDE RESISTANCE IN-FIELD STRAINS OF PECTINOPHORA-GOSSYPIELLA (SAUNDERS) IN CHINA AND EFFECT OF SYNERGISTS ON DELTAMETHRIN AND PARATHION-METHYL ACTIVITY

Filter-paper residual toxicities of some insecticides used extensively in China were determined during 1994 using newly hatched (within 30 m in) larvae of four Pectinophora gossypiella (Saunders) strains. The st rains were field collections collected in the Yangtze River cotton-bel t areas. Compared with the susceptible laboratory strain from Qunli (L ishui County, Jiangsu province), the four held strains from Anqing (An hui province), Jiangling (Hubei province), Cixi(Zhejiang province) and Tongzhou(Jiangsu province) had developed 185-, 6.7-, 698- and 249-fol d resistance, respectively, to deltamethrin. Cixi and Tongzhou held st rains had also developed 103- and 94-fold resistance to fenvalerate, a nd 10- and 3.6-fold resistance to parathion-methyl. Percentage of surv ivors at diagnostic dosage for deltamethrin showed that the strains fr om Anqing, Jiangling, Cixi and Tongzhou had 87.2, 18.3, 90.1 and 74.6% resistant individuals respectively. Cixi and Tongzhou field strains h ad 88.9 and 65.3% resistant individuals after application of parathion -methyl, which was consistent with the corresponding resistance ratios . Studies of the effect of synergists piperonyl butoxide (PBO), triphe nyl phosphate (TPP) with deltamethrin and parathion-methyl in Cixi, An qing and Tongzhou field strains suggested that metabolic resistance me chanisms such as carboxylesterases (CarE) and mixed function oxygenase s (MFO) were involved in parathion-methyl resistance, but not in delta methrin resistance.