Acute Toxicity of Pesticide Dichlorvos and Herbicide Butachlor to Microhyla ornata Tadpoles

Dichlorvos and butachlor are the most commonly used pesticide and herbicide in China. However, little is known about the toxic effects on amphibians. Feeding stage of Microhyla ornata tadpoles was exposed to dichlorvors and butachlor for 48 hours in static-renewal acute toxic tests. Following range-finding tests, seven concentrations of either dichlorvos or butachlor were determined using equal logarithmic basis. The results showed that the 24-h and 48-h LC_ 50 values of the tadpoles for dichlorvos were 3.91 μl/L and 1.97 μl/L, while for butachlor were 3.37 μl/L and 1.88 μl/L. In the test, the toxicity of butachlor against Microhyla ornata tadpoles was slightly more toxic than that of dichlorvos.