Toxicity Evaluation of Twenty-five Pesticides to Bombyx mori and Observation of Toxi Symptoms

The acute toxicities of 25 pesticides to silkworm,Bombyx mori,were evaluated in laboratory by using the leaf dipping method including 18 pesticides,4 antiseptics,2 herbicides and 1 phytohormone.The toxi symptoms of silkworms after treatment of pesticides were systematically observed.The results indicated that the LC50 s of emamectin benzoate,β-cypermethrin etc.14 insecticides were lower than 0.5 mg/L,belonging to virulent toxicity grade;those of molosultap and methoxyfenozide 2 insecticides were 0.549 3 mg/L and 0.604 0 mg/L,respectively,belonging to high toxicity grade;those of chlorfenapyr and diafenthiuron 2 pesticides were 72.370 mg/L and 27.824 mg/L,belonging to middling toxicity grade and relatively lower than other insecticides.In the 7 pesticides including 4 antiseptics,2 herbicides and 1 phytohormone there was only 1 antiseptic belonging to medium toxicity grade and the other belonging to low toxicity grade.The observation of toxicosis symptoms of 18 insecticides on silkworm showed that different pesticides displayed similar symptoms like vomitive,distorted,"C" or "S" shaped and repose etc.While the toxicosis process of the incretion insectcides and chitin synthesis inhibitors were relatively slow.