D3356: Toxicity of pesticides to citrus mealybug natural enemies

Citrus mealybug (Planococcus citri [Risso]) (Hemiptera: Pseudococcidae) is a polyphagous pest that affects citrus and various other plants. Mealybugs are small, soft-bodied, oval-shaped insects covered in a white, waxy powder and are often found in clusters. They cause damage by sucking plant sap, yellowing of leaves and fruits, and indirect damage by honeydew and sooty mold. Although present in citrus systems in California, mealybugs were kept in check by natural enemies and did not require targeted management until 2020. In recent years, mealybugs have become an increasingly challenging pest problem. Field trials identified several pesticides registered for citrus in California are toxic to citrus mealybug and can be used for near-term management. However, the toxicity of insecticides on mealybug predators/parasitoids is an important factor to consider in integrated pest management (IPM) strategies. We conducted laboratory bioassays to evaluate the acute toxicity of five pesticides: abamectin, acetamiprid, azadirachtin, afidopyropen, and spirotetramat. Two life stages: larvae and adults of a mealybug predator Cryptolaemus montrouzieri and the adult stage of a mealybug parasitoid, Anagyrus vladimiri were tested. Fully opened leaves were dipped in pesticide solutions, air dried, and natural enemies were released. Mortality was assessed at timed intervals, 2, 4, 8, 12, 24, and 48 hours after exposure to treated leaves. Results are discussed in the context of IPM of citrus mealybug.