Toxicity of greenhouse pesticides to multicolored Asian lady beetles, Harmonia axyridis (Coleoptera: Coccinellidae)

A variety of insecticides, acaricides, and fungicides is used in greenhouses to protect plants. As predacious ladybirds are also used to control aphids, it is important to understand the effects of such pesticides on these beneficial insects. We examined the susceptibility to all developmental stages of the multicolored Asian ladybird beetle, Harmonia axyridis (Pallas), to 12 agents: four insecticides, four acaricides and four fungicides. Etofenprox and acetamiprid were highly toxic to most developmental stages, and also in the adult at 200 mg [AI]/L and 40 mg [AI]/L (recommended dosages for aphid control). Thiamethoxam caused knockdown of larvae, pupae, and adults; however, most recovered within 24 h. Imidacloprid, applied at 50 mg [AI]/L, produced LC50 values of 30.3 and 190.2 mg [AI]/L for 3rd and 4th instars, respectively. Abamectin was highly toxic to eggs, larvae, pupae, and adult ladybirds at rates under 18.4 mg [AI]/L. However, recommended doses of other acaricides were very safe to all stages except for the egg stage of H. axyridis. The fungicide pyrazophos was highly toxic to eggs and larvae at a rate much lower than the recommended dose, while other tested fungicides were not toxic to any of the ladybird stages at rates over 1000 mg [AI]/L. Generally, the 1st and 2nd instars of H. axyridis were very sensitive to most of the tested insecticides and acaricides. Fungicides, on the other hand, were generally harmless to H. axyridis.