Influence of metalaxyl fungicide seed treatment on severity of rootworm (Diabrotica spp.) damage to corn (Zea mays) under no-tillage conditions

Fungicide seed treatments and soil insecticides were used in no-till fields to improve plant stand, decrease corn rootworm injury ratings, and increase yields in a 2-year study at two locations in Illinois. Throughout the study, the addition of the insecticide chlorpyrifos consistently decreased corn rootworm injury ratings. The fungicide seed treatment metalaxyl significantly decreased plant stand loss and reduced the number of stunted plants. The addition of metalaxyl to captan as a seed treatment significantly (P≤0.05) reduced the rootworm injury ratings compared to captan alone in three of eight comparisons when chlorpyrifos was not applied for rootworm control. In the absence of chlorpyrifos, metalaxyl never reduced rootworm injury ratings below a 3.0. For this reason, metalaxyl should not be considered as an alternative to insecticides for rootworm control, but should be recognized by corn breeders and others as having a possible effect on a hybrid or inbred's susceptibility to rootworms.