Effects of chlorpyrifos and abamectin on development of the immature stages of Cryptolaemus montrouzieri Mulsant (Coleoptera: Coccinellidae)

The lethal and sublethal effects of chlorpyrifos+oil, abamectin, and chlorpyrifos+abamectin+oil on the immature stages of Cryptolaemus montrouzieri Mulsant were investigated under laboratory conditions. chlorpyrifos was applied at 500, 1000 and 2000 ppm with 1% oil and abamectin at 500, 100, and 200 ppm concentrations on fourth instar larvae through three exposure methods, including topical direct contact, residual contact and feeding on sprayed preys. The eggs of C. montrouzieri treated via dipping in pesticide solutions. Dipping eggs in pesticide solutions affected significantly their hatching percent, first instars larvae survival, and pupa weight. The lowest egg hatching percent (29 percent) and pupa weight (9.8 mgr.) were observed in chlorpyriphos 2000 ppm+abamectin 200 ppm+oil. Survival of the fourth instar larvae and pupa developmental period and weight were also significantly affected in each exposure method. The lowest survival of fourth instar larvae (50 percent) and longest pupa duration (7.0 days) were obtained in topical contact with chlorpyriphos 2000 ppm+abamectin 200 ppm+oil. In conclusion, because of the adverse effects of chlorpyriphos on the development of immature stages of the ladybird, replacing it with a safer pesticide is necessary to increase the compatibility of biological and chemical control programs in citrus orchards of northern Iran.