Insecticidal Control of Lepidopteran Pests in Sweet Corn, 2017

The objective of this experiment was to evaluate efficacy of insecticidal treatments for control of lepidopteran pests in sweet corn in Minnesota. On 26 Jun, ‘Providence’ was planted at the University of Minnesota Research and Outreach Center at Rosemount, MN. Fifteen treatments were arranged in an RCB design with four replications. Plots consisted of two rows 25-ft (7.6 m) long with 30-inch (0.8 m) row spacing. A single skip row separated treatments and 10-ft alleys– (3.04 m) separated replicates. Insecticide applications were made with a CO₂-pressurized backpack sprayer with a 3 ft (0.9 m) 2-nozzle boom with 20-inch (0.5 m) nozzle spacing. Nozzles were XR-Teejet 8002 flat fan nozzles with no screen. The sprayer was calibrated to deliver 25 gpa (233.8 liter/ha) at 35 psi (242 kPa). The ear zone of each row of the 2-row plot was treated beginning at 48% silk. A total of four applications were made on the following dates: 2 Aug and 1, 8, and 14 Sep.

On 21 Sep, 20 primary ears per plot were harvested by skipping the first 3 ears on either end of a row and arbitrarily selecting 10 primary ears from each row. Ears were evaluated for both corn earworm (CEW) and European corn borer (ECB) and data recorded for total number of larvae, larval size and location, and feeding damage (number of kernels). Ears were also rated for both fresh market and processing marketability. All data were analyzed using ANOVA. Proportion data were arcsine transformed and count data were square root transformed prior to analysis. Untransformed means are presented. Means were separated using a protected LSD (P = 0.05).

Notably, no ECB larvae were detected in any treated ears or the untreated check. Therefore, the main pest in this trial was CEW with a mean total CEW larval density of 0.49 per ear in the untreated check (Table 1). All treatments provided a significant reduction in CEW compared with the untreated check. Percentage of marketable ears for both fresh market and processing was significantly higher for all treatments compared with the untreated check. Kernel feeding damage was primarily on the tip of the ear and was significantly lower in all treatments compared with the untreated check. Phytotoxicity was not observed among treatments.

This research was supported by industry gifts of pesticide and/or research funding from Winfield Solutions, FMC Corp., Syngenta Crop Protection, and Valent and Dupont.