Contamination by systemic insecticide harms the dispersal ability of the lady beetle Hippodamia variegata

The lady beetle Hippodamia variegata (Coleoptera: Coccinellidae) is a generalist predator in Xinjiang, China, preying on aphids such as Aphis gossypii (Hemiptera: Aphididae) and other arthropods in agricultural ecosystems. Imidacloprid, the most widely used neonicotinoid insecticide globally, is commonly used to manage sucking pests such as aphids; however, it can have detrimental sublethal effects on some natural enemies. The development of IPM programs against pests requires an evaluation of the side effects of insecticides on important natural enemies. We found that exposure to aphids treated with sublethal levels of imidacloprid (LC₂₀ and LC₅₀) reduced longevity, fecundity, and flight performance of H. variegata adults. Specifically, exposure to aphids treated at the LC₅₀ level reduced the flight distance and flight duration of the lady beetle by 81.9 % and 78.5 %, respectively, compared with the control group. Carbohydrate metabolism in lady beetles fed aphids in the LC₂₀ and LC₅₀ groups was significantly impaired, leading to higher trehalose and glycogen content compared to beetles in the control group that were fed untreated aphids. Moreover, the activity of metabolism enzymes was significantly reduced, although there was no significant effect on the levels of metabolism enzymes. In mark-release-recapture experiments conducted in cotton fields, sublethal concentrations of imidacloprid significantly reduced the dispersal distance of these beetles during the first two days after release. These results demonstrate that sublethal concentrations of imidacloprid have a negative impact on the flight dispersal ability of H. variegata, which could impair the regional biological control services provided by this predator.