Effectiveness of Acephate and Carbofuran Seed Treatments to Control the Black Cutworm, Agrotis ipsilon (Lepidoptera: Noctuidae), on Field Corn

Abstract

Studies were conducted in the laboratory, greenhouse, and field to determine the effectiveness of acephate and carbofuran seed treatments to control fourth- to fifthinstar black cutworm (BCW), Agrotis ipsilon (Hufnagel), on field corn. Acephate incorporated into BCW diet was 4- to 5-fold more toxic than carbaryl, which is currently registered as a bait for BCW control. Residues of acephate, applied as a seed treatment to corn, were essentially confined to the leaves and seeds, and only 10% of the acephate was metabolized to methamidophos. Laboratory bioassays with field-grown, one-leaf-stage corn seedlings from eight field trials showed that acephate (at dosages of 0.004–0.008 g [AI]/g seed) was more effective in fall plantings (when less precipitation fell between planting and bioassay) than in spring plantings (which received more rainfall). In general, low recoveries of acephate residues from corn seedlings were coincident with high rainfall conditions. Carbofuran was evaluated only in fall plantings and was effective against BCW larvae. In a field-barrier test conducted in the fall when no precipitation occurred between the time of planting and infestation of larvae, both acephate and carbofuran seed treatments significantly reduced cutting damage compared to untreated seed. However, in a field-barrier test conducted in the spring with cumulative precipitation of 12.5 cm between planting and infestation, acephate seed treatments did not significantly reduce cutting damage compared to untreated seed. In greenhouse tests, highest BCW mortality and acephate residues were associated with low soil moisture. These studies suggest that acephate seed treatments will not effectively protect corn seedlings against attack by BCW larvae uncler levels of precipitation normally encountered in the spring in the midwestern corn belt. Limited experiments suggest that carbofuran might be more effective than acephate under these conditions. However, bird mortality and lower seed germination resulted when this compound was used as a seed treatment.