Effects of chlorpyrifos and abamectin on survival and fecundity of the adult Cryptolaemus montrouzieri Mulsant (Coleoptera: Coccinellidae)

Cryptolaemus montrouzieri Mulsant is the most important predator of the mealybugs in citrus orchards of northern Iran. In this study, the lethal and sublethal effects of different doses of chlorpyrifos+oil, abamectin, and chlorpyrifos+abamectin+oil on the adult ladybeetles were investigated under laboratory conditions. Each pesticide was applied at 25, 50 and 100% recommended field application rates (i.e. chlorpyrifos at 500, 1000 and 2000 ppm and abamectin at 50, 100 and 200 ppm concentrations) with 1% oil on 7-day old female ladybirds through three exposure methods, including topical direct contact, residual contact and feeding on sprayed preys. 24, 48, and 72 hours after treatment the parameters such as survival rate, mean of daily oviposition, and hatching percent of the eggs were measured. The results showed that chlorpyrifos+abamectin+ oil affected the survival rates through all three exposure methods, whereas chlorpyrifos effect on the survival rate was only observed in topical contact, and abamectin had no adverse effect on the adult survival. Among all treatments, chlorpyrifos 2000+abamectin 200 ppm had the highest adverse effect on female ladybird survival (with 16 percent mortality). In contrast to survival rate, mean daily oviposition, and egg hatching percent were significantly reduced in all three treatments and exposure methods, and this reduction continued until 72 hours after exposure. The lowest mean of daily oviposition (8.2 eggs per female) was observed 24 hours after feeding on preys treated with chlorpyrifos 2000 ppm+ abamectin 200 ppm+oil, and the lowest egg hatching rate (57.9 percent) was recorded 24 hours after topical contact with the same treatment. In conclusion, using field rates of chlorpyrifos and chlorpyrifos+abamectin with oil adversely affect survival and fecundity of the ladybird. So, it is necessary to use of pesticide in suitable time and spraying to increase compatibility between pesticide application and ladybird activity, in citrus orchards.