Comparative toxicity of coffee insecticides to the green lacewing Chrysoperla externa in laboratory and persistence trials

Abstract

The green lacewing Chrysoperla externa (Hagen) (Neuroptera: Chrysopidae) is a generalist predator with a diet including major coffee pests. Aiming at a harmonious integration of biological and chemical control in coffee production systems, ecotoxicology studies are required to provide information on insecticide harmfulness toward natural enemies. We investigated the side effects of five coffee insecticides sprayed on eggs and third-instar larvae (L3) of C. externa. The assessed endpoints included C. externa viability (egg hatchability and L3 survival), developmental time, cycle completion, and body weight, sex ratio (female proportion) and accumulated oviposition of adults derived from the treated stages. Cyantraniliprole reduced viability of treated eggs, whereas abamectin prolonged the developmental time and reduced the oviposition of adults reared from the treated L3. In the F1 generation from treated L3, abamectin diminished egg viability and cycle completion and interfered with sex ratio and adult weight. Apart from these results, metaflumizone caused the most striking effects on C. externa by producing high L3 mortality (96%). The hazardousness of this compound, however, was dismissed in persistence bioassays (L3 exposure to aged residues in coffee leaves), indicating that metaflumizone requires direct spraying to kill C. externa. These findings allow us to conclude that while the other compounds (abamectin, abamectin + chlorantraniliprole, chlorantraniliprole and cyantraniliprole) are intrinsically safer for C. externa, metaflumizone applications should be performed in periods of low C. externa activity in plants to avoid direct predator exposure.