Studies On Resistance Selection And Mechanisms Of Pieris Rapae To Chlorfenaypr

Selection of larvae of the cabbage worm, Pieris rapae (L.), with chlorfenapyr increased resistance. After 7 generations of selection pressure, resistance to chlorfenapyr was over 15.576-fold in this strain compared with the unselsected parental stain. A susceptible strain was obstained by two-generation selection. And its LD50 was 0.000502g/larva.Based on the method descryibed by Tabashnik(1992), the realized heritability (h2) of resistance to cabbage worm was estimated to be 0.3543. The rate of reistance development in cabbage worm was predicted according to the realized heritability (h2), and its result indicated that cabbage worm had a little potentiality of high resistance on the conditions of field.Careful research was taken to two different strains in the terms of developmental and reproductive characterstics under artifitial climate condition. Life tables of the resistant strain and the susceptible strain constructed. The results indicated that the resistant strain had some disadvantage in the developmental and reproducetive characteristics when compared with the susceptible strain. The resistant strain showed distinct disadvantage in the emergence rate and average eggs per female.Great difference was found between the two strains in rate of aspiration after treated by insecticide chlorfenapyr, the resistant stain showed little variation treated by insecticide, but the susceptible strain showed great decrease treated by insecticide. Two strains to the activity of 3 enzymes (esterase, carboxylesterase and glutathione-S-transferase) were determined. The results showed that the activity ofesterase and carboxylesterase of the resistant strain was no distinct difference compared with those of the susceptible strain, but the activity of glutathione-S-transferase of the resistant strain was lower than that of the susceptible strain.