Lethal and sub-lethal effects of imidacloprid on the aphidophagous coccinellid hippodamia variegata

Hippodamia variegata is one of the most abundant ladybird species in Greece, preying on several aphid species and other arthropods, of which many are pests of cultivated plants. Imidacloprid, a neonicotinoid insecticide, is commonly used for controlling sucking insects; at the same time, however, it can cause various sub-lethal effects on non-target organisms. The development of IPM programs against pests requires an evaluation of the side effects of insecticides on natural enemies. We evaluated the sub-lethal effects of imidacloprid on H. variegata. Our results demonstrate that imidacloprid at a LC10 (3.92 mg (a.i.) L-1 and LC30 (8.69 mg (a.i.) L-1) decreased adult longevity and survival rate. In addition, demographic parameters, such as the intrinsic rate of increase (r), finite rate of increase (lambda) and net reproductive rate (R-0), were reduced when exposed to sub-lethal concentrations of imidacloprid. These results demonstrate a negative influence of imidacloprid at sub-lethal concentrations on H. variegata which could reduce biological control services provided by this predator. (C) 2019 Elsevier Ltd. All rights reserved.