TOXICITY OF INSECTICIDES TO LARVAE OF THE MEXICAN CORN-ROOTWORM (COLEOPTERA, CHRYSOMELIDAE) IN A SOIL BIOASSAY

Toxicity of insecticides typically used to protect corn roots from fee ding by Mexican corn rootworm, Diabrotica virgifera zeae Krysan and Sm ith, larvae were established using a soil bioassay. There was a 23-fol d difference in toxicity of insecticides for larvae of the Mexican cor n rootworm. Carbofuran had significantly lower LC(50) and LC(95) value s in an alkaline soil from south central Texas compared to a nearly ne utral pH silty clay loam soil from South Dakota. Lack of ''control'' b y soil applied insecticides was not due to higher tolerance by larvae of this Diabrotica spp.