Insecticidal Control of Corn Earworm and European Corn Borer in Minnesota Sweet Corn, 2016*

The objective of this experiment was to evaluate the efficacy of insecticide treatments for the control of lepidopteran pests of sweet corn in Minnesota. A conventional sweet corn hybrid, ‘EX 08767143’, was planted 27 Jun at the University of Minnesota Research and Outreach Center at Rosemount, MN. Nineteen treatments were arranged in an RCB design with four replications. Plots consisted of 2 rows 25 ft (7.6 m) long with 30 in. (0.8 m) row spacing. A single skip row separated treatments and 10 ft. alleys (3.04 m) separated replications. Treatment applications were made using a CO₂ pressurized backpack sprayer with a 3-ft (0.9 m) 2-nozzle boom with 20 in. (0.5 m) between nozzles. Nozzles were XR-Teejet 8002 flat fan nozzles with no screen. The sprayer was calibrated to deliver 25 GPa (233.8 l/ha) at 35 psi (242 kPa). The ear zone of each row of the 2-row plot was treated beginning at 12.5% silk. A total of four applications were made on the following dates, 22 and 26 Aug and 2 and 9 Sep.

Twenty primary ears per plot were harvested and evaluated 15 Sep. Total number of larvae, larval size and location, and feeding damage (number of kernels), were recorded for both CEW and ECB. 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).

Mean total CEW and ECB larval densities were 1.51 and 0.01 per ear, respectively, in the untreated check (Table 1). There were no significant differences in ECB larval populations in any treatments compared with the untreated check because of low background densities of ECB in Minnesota. The primary pest in this trial was CEW and all treatments provided a significant reduction in CEW populations 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 limited to the ear tip and was significantly lower in all treatments compared with the untreated check. Phytotoxicity was not observed among the treatments.

Author notes