Toxicity and field persistence of thiamethoxam and dinotefuran against cabbage aphid, Brevicoryne brassica L. (Homoptera: Aphididae) under laboratory and field conditions

Abstract

Cabbage aphid, Brevicoryne brassica L. is one of the most destructive and economically important insect pests of canola (Brassica napus L.) worldwide including Egypt. Few information is available on the effect of neonicotinoid insecticides (thiamethoxam and dinotefuran) against cabbage aphid on canola fields in Egypt, particularly in Assiut Governorate. Thus, this study was carried out to evaluate the toxicity and field persistence of thiamethoxam and dinotefuran against cabbage aphid under laboratory and field conditions. Under laboratory condition, thiamethoxam was showed high toxic effect against adult field strain of cabbage aphid with LC₅₀ values, 84.10, 6.60 and 3.21 mg/L after 24, 48 and 72 hrs post treatment, respectively.  In addition, dinotefuran also exhibited toxic effect against this pest but less than thiamethoxam where the LC₅₀ values were 300.50, 43.85 and 6.74 mgL^-1, respectively after the periods of exposure. Based on the relative potency values, thiamethoxam was more effective than dinotefuran with 3.6, 6.6 and 2.1 fold after the periods of exposure. Under field condition, both thiamethoxam and dinotefuran exhibited efficiency against cabbage aphid population on canola plants after one, three, seven, fifteen and twenty-one days of treatments but thiamethoxam was more efficient than dinotefuran. Cabbage aphid reduction percent were 62.07, 89.80, 96.02, 96.59 and 94.55% for thiamethoxam and 8.58, 65.63, 86.77, 93.92 and 71.18% for dinotefuran after periods of exposure. The obtained data from this study indicated that thiamethoxam have a high toxicity effect against cabbage aphid under laboratory and field conditions. Based on our results, we suggest using thiamethoxam for cabbage aphid control in canola fields in Assiut Governorate, however more trails are needed about which in other Egyptian Governorates.