Effects of sublethal concentrations of some biorational insecticides in predation potential of Cryptolaemus montrouzieri on Dactylopius opuntiae

Abstract

Assessments of compatibility between targeted insecticides and beneficial organisms are important for integrated pest management programs. In this study, we investigated the effect of some biorational insecticides: D-limonene (applied at 1\xa0g/L), mineral oil (applied at 20\xa0g/L), potassium salts of fatty acid (applied at 0.4\xa0g/L), pyriproxyfen (applied at 0.25\xa0g/L), and potassium salts of fatty acid (C7-C18) (applied at 3\xa0g/L) on the functional response of Cryptolaemus montrouzieri (Mulsant) feeding on Dactylopius opuntiae (Cockerell) females under controlled conditions (26\xa0°C). Previous experiments established that the insecticide rates used in the present study were sublethal, as they did not cause short-term mortality to the predator. In the absence of insecticides, the predator exhibited a type II functional response. All insecticide treatments in this study did not hamper the ladybird functional response, but it altered the shape of the curve compared to the control (tap water). Our results showed that all insecticides treatments residues do not have lethal effects on C. montrouzieri adult, and do not affect significantly his predation. Pyriproxyfen and potassium salts of fatty acid (C7-C18) seem to be the least compatible with C. montrouzieri as it led to both a significant reduction of attack rate (0.01–0.05) and an increase in handling time (2.57–12.77\xa0h). In contrast D-limonene (applied at 1\xa0g/L), mineral oil (applied at 20\xa0g/L) were the most compatible with the predator, as it led to both a significant increase in attack rate (0.05–0.12) and a decrease in handling time (3.91- 5.71\xa0h).