toxicity of some biorational and conventional insecticides to cotton bollworm, helicoverpa armigera (lepidoptera: noctuidae) and its ectoparasitoid, habrobracon hebetor (hymenoptera: braconidae)

insect growth regulators and spinosyns which are physiologically and ecologically selective, respectively, have been investigated as replacements or complements to non-selective conventional insecticides. the effects of diflubenzuron, hexaflumuron, profenofos, spinosad and thiodicarb were assessed on the 1st instars of cotton bollworm, helicoverpa armigera (hã¼bner) using dietary and leaf disc bioassay methods. based on modes of action of the insecticides tested, the mortalities were recorded after 24 h in profenofos, thiodicarb and spinosad experiments and after 120 h in hexaflumuron and diflubenzuron treatments. the lc50 values for diflubenzuron, hexaflumuron, profenofos, spinosad and thiodicarb in dietary method were 595.05, 0.31, 3.69, 0.13 and 11.2 mg ai/l; and in leaf disc method, they were >2000, 0.46, 9.55, 0.2 and 15.52 mg ai/l, respectively. the effects of these insecticides on adult habrobracon hebetor say, an ectoparasitoid of cotton bollworm were tested using residual method. the mortalities were recorded after 24 h in all treatments. the lc50 values for diflubenzuron, hexaflumuron, profenofos, spinosad and thiodicarb for females were >2000, >2000, 12.44, 15.64 and 81.04 mg ai/l, respectively and for males, they were >2000, >2000, 6.91, 11.73 and 40.39 mg ai/l, respectively. in this study spinosad and hexaflumuron seemed to be more useful than the other insecticides due to their higher toxicity to h. armigera and lower toxicity to h. hebetor.