Evaluation of Selected Insecticides for Control of Corn Earworm in Grain Sorghum, 2018

Several insecticides were evaluated for control of corn earworm in grain sorghum at the Research and Education Center at Milan, TN. Grain sorghum was planted on 15 Jun. The test was arranged in an RCB design with four replicates. Individual plots were 12.5 × 40 ft (5 rows with 30-inch centers). Treatments were applied with a high clearance sprayer calibrated to deliver 9.4 gpa at 40 psi with 8001 flat fan nozzles. Foliar application was made 21 Aug. Plots were sampled by bending and vigorously shaking 10 sorghum heads from the center two rows of each plot into a standard 15-inch sweep net and counting larvae. Insect control was evaluated 27 Aug, 6 days after treatment (6 DAT) and 31 Aug (10 DAT). Yield data were collected 27 Nov by harvesting two center rows of each plot with a plot combine. Data were subjected to ANOVA and means were separated using a protected Least Significant Difference (LSD).

All insecticide treatments significantly reduced the numbers of small, large, and total corn earworm larvae at both evaluation timings compared with the untreated check (Table 1). At 6 DAT, all insecticides provided similar control of small and large corn earworm, but plots treated with Blackhawk had more total corn earworm than all other insecticide treatments. By 10 DAT, plots treated with Besiege alone or coapplied with a fungicide (Headline) had fewer small corn earworm than those treated with Mustang Maxx. Mustang Maxx resulted in significantly more large and total corn earworm larvae than all of the other insecticide treatments at 10 DAT. There were no significant differences in yield among treatments, and the addition of a fungicide did not affect yield. No phytotoxicity was observed with any treatment.

This research was partially supported by industry gifts of pesticide and seed.