Aerial Spray Deposition on Corn Silks Applied at High and Low Spray Rates
Corn earworm is a major pest of sweet corn, especially when grown organically. Aerial application of insecticides is important for both conventionally- and organically-grown sweet corn production as sweet corn is frequently irrigated to assure return on investment given the high production costs. Aerial insecticide application costs can be minimized through use of reduced spray rates if insecticide efficacy can be maintained at the lower spray rates. The objectives of the study were to characterize deposition on field corn silks when applied at 47.9 L/ha (with VMDs at 230 and 400 μm) and 86.2 L/ha (with VMD at 400 μm) spray rates. Applications of the bioinsecticide, Gemstar®, and the insecticide, Entrust®, which are both approved for use in organic production, were made over three different fields. The amount of spray material deposited on individual silks for each treatment was determined. Deposition of spray material on the silks was very similar across all application treatments. Overall, the 86.2 L/ha rate resulted in the greatest deposition of active material on the corn silks. At the 47.9 L/ha rate, the smaller droplet size sprays resulted in less deposition than the other treatments.