Oral Toxicity and Risk of Five Insecticides to Honeybees

Two methods,"small beaker" and "feeding tube",were adopted to measure the oral toxicity of five insecticides to honeybees,including 50% chlorfenapy WG,1% methylamino abamectin benzoate EC,80% fipronil WG,50 g/L fipronil SC, and 10% abamectin+pyridaben EC.As measured by the method of "small beaker",the 48 h LC50 values of the five insecticides were 21.3,0.490,0.112,0.0757,and 0.488 mg/L,respectively,while measured by the method of "feeding tube",the 48 h LC50 values were 134,0.730,1.33,0.668,and 1.54 mg/L,respectively.The result suggested that the method of "small beaker" overestimated toxicity of the 5 insecticides to bees compared with that of "feeding tube".If it was counted by average amount of intake,the 48 h LD50 values of the five insecticides,resulting from the method of "feeding tube",could be expressed as: 1.34,0.007 30,0.013 3,0.005 37,and 0.015 4 mg/bee,respectively.According to a category of toxicity for bees,which was adopted by administrative department of pesticides in China,50% chlorfenapy WG was moderately toxic,1% methylamino abamectin benzoate EC,10% abamectin+ pyridaben EC,80% fipronil WG and 50 g/L fipronil SC were extremely toxic to bees.When a parameter of hazard quotients (HQ) was introduced to scale the risk of the 5 insecticides to bees,the HQ values were calculated as 84.0, 205,3 247,3 609,and 8 939,respectively.This suggested that the 5 insecticides mentioned above might impose hazards to bees if they were applied in the field.Character and applicabilitie of the two methods were discussed.