Toxicity of spirotetramat, spiromesifen, thiamethoxam + lambda-cyhalothrin and azadirachtin on cabbage aphid, Brevicoryne brassicae (Hem.: Aphididae)

The cabbage aphid, Brevicoryne brassicae is one of the most important insect pests of cabbage in Iran. Chemical insecticides are considered as the key tools in controlling this pest. However, a major issue with these synthetic chemicals is cabbage contamination with their residues and as well as development of resistance by the pest. The present study evaluated the toxicity of spirotetramat, spiromesifen, thiamethoxam + lambda-cyhalothrin and azadirachtin to the cabbage aphid through contact, systemic and contact-systemic methods. Different bioassay methods were applied to assess the probable differences in toxicity of these insecticides.  The results showed that thiamethoxam + lambda-cyhalothrin was more effective than three other insecticides to adult cabbage aphid with contact method and was more lethal than the spirotetramat in the systemic method on adult cabbage aphid. Spiromesifen was less effective than three other insecticides on adults in contact-systemic method. Thiamethoxam + lambda cyhalothrin was more effective than the spiromesifen on the nymphs by contact than spirotetramat and azadirachtin by systemic methods. In the contact-systemic method, thiamethoxam + lambda-cyhalothrin was more effective than spiromesifen and azadirachtin on nymphs. The results indicated higher toxicity of thiamethoxam + lambda-cyhalothrin on the adult and nymphal stages of B. brassicae. Hence, it can be recommended in integrated management programs for the control of this pest.