Safety evaluation of eight commonly used insecticides ondifferent stages of Hippodamia variegata (Goeze)

Hippodamia variegata (Goeze) is one of the dominant predatory natural enemies in Xinjiang cotton fields. In order to clarify the toxicity of eight commonly used insecticides in cotton fields to eggs, larvae, pupae, and adults of H. variegata, the effects of different doses of insecticides on the survival, hatching, and eclosion rate of H. variegata were measured by filter paper contact and dipping methods. The results showed that avermectin had the lowest toxicity to the eggs and pupae of H. variegata with the LC₅₀ values of 9.36 and 20.98 mg/L, respectively, and the highest toxicity to the larva with the LC₅₀ value of 4.68 mg/L. The highest toxicity of nitenpyram to the eggs and pupae was observed with the LC₅₀ values of 1.16 and 1.02 mg/L, respectively. Imidacloprid showed the lowest toxicity to adults and larvae with the LC₅₀ values of 665.50 and 460.51 mg/L, respectively. The toxicity of spirotetramat to adults was the highest with the LC₅₀ value of 5.67 mg/L. After treatment with different insecticides, the hatching rate and eclosion rate of H. variegata gradually decreased with the increase of insecticide dose, and the mortality rate gradually increased. Imidacloprid, acetamiprid and pymetrozine were safe for adults of H. variegata. Imidacloprid, flonicamid, and pymetrozine were safe for the larvae of H. variegata. The safety of nitenpyram and spirotetramat was poor against eggs, larvae, pupae, and adults of H. variegata. In the control of pests in cotton fields, we should not apply or apply low doses of nitenpyram and spirotetramat, and appropriately apply imidacloprid and acetones. Try to bypass the occurrence peak period of each natural enemy insect state.