| Insecticide resistance in cotton bollworm in cotton cultivated areas of Jiangsu and Hebei province Resistance of cotton bollworm to three kinds of insecticide was determined in cotton cultivated areas in Jiangsu and Hebei province. Topical application bioassays with 3rd-instar larvae showed low to moderate resistnace level to profenofos and phoxim with 5.4-28 fold resistance in populations collected from Jiangpu county in Jiangsu province and Weixian and Qiuxian county in Hebei province, high to super high resistance level to fenvalerate, methomyl and cyhalothrin with 52.7~66, 52.7~996 and 118~1318 fold resistance respectively, super high resistance level to deltamethrin with 166~835 fold resistance. In 2003, the resistance to all insecticides tested was increased in the population from Jiangpu county, however, the resistance was decreased in the population from Weixian county and lower than in the population from Jiangpu county.Selection and risk assessment of resistance to profenofos in three populations of cotton bullworin, Helicoverapa armigera Three populations of cotton bollworm, Helicoverpa armigera, DTR, WXR and QDR, were continuously selected for resistance to profenofos for 4~20 generations, resistance to profenofos had increased by 5.8-, 1.2- and 4.7-fold, respectively. The realized heritability of resistance and resistance risk of three populations to profenofos were evaluated using threshold trait analysis. The realized heritability of resistance to profenofos was 0.1209, 0.1011 and 0.2513, respectively. Theoretically, to obtain a 10-fold increase in resistance requires 15~12 generations in DTR, 18~14 generations in WXR and 7~6 generations in QDR for profenofos under selective pressure of 80%~90% mortality for each selective generation. These results provide some basis for the management of pesticide resistance in cotton bollworm.Cross-resistance and the synergism of three synergists in profenofos resistant strain of the cotton bollworm After artificial selection for resistance to profenofos for 30 generations, the resistant strain had middle level resistance to profenofos (17.4-fold), significant cross resistance to MVP II, monocrotophos and phoxim with increased resistance ratio of 9.2-, 8.1- and 4.6- fold, and low level cross resistance to methomyl, deltamethrin and cyhalothrin with increased resistance ratio of 2.9-, 2.6- and 1.8- folds.After selected for 42 generations, the resistant strain had high level resistanc to profenofos (51.4-fold), the cross resistance to MVP II and methomyl were increased and the resistance ratio were increased to 28- and 11- folds respectively, and the cross resistance to monocrotophos, phoxim, deltamethrin and cyhalothrin were not changed.Synergism ratios of PBO, SV1 and DBF to profenofos in DTK strain were 0.1,0.9 and 1.0, respectively, which implied that esterase appeared to be one of the important resistant factor in this laboratory selected resistant strain. Carboxylesterase activity was significantly higher in the profenofos resistant strain than that of the profenofos susceptible strain when a -NA were used as substrates, futher polyacrylamide gel electrophoresis (PAGE) analysis revealed that the esterase from resistant and susceptible strains involves different isoenzyme composition which implied that the changes of carboxylesterase isoenzymes is involved in the mechanisms for profenofos resistance in cotton bollworm.The super high resistant strain of cotton bollworm selected with Bt cotton leaves for >60 generations showed siginifiant cross resistance to 20% MVPII liquid formulation, but no cross resistance to profenofos, methomyl, high effect cypermethrin, cyhalothrin, mythl-parathion, phoxim and cyhalothrin + phoxim.Genetics and the Relative Fitness of Resistance to Profenofos in the Cotton Bollworm, Helicoverpa armigera Inheritance mode of resistance to profenofos in the cotton bollworm, Helicoverpa armigera, and the relative fitness of the resistant, susceptible strains and reciprocal cross progenies were studied in the laboratory. The... |
