Evaluation of Selected Insecticides for Control of Sugarcane Aphid in Grain Sorghum, 2015 *

Selected insecticide treatments were evaluated for control of sugarcane aphid in grain sorghum at the Research and Education Center at Milan (Milan, TN). Grain sorghum was planted on 17 June. The test was arranged in an RCB design with four replicates. Individual plots were 12.5 by 30 ft. Treatments were applied with a high clearance sprayer calibrated to deliver 9.4 GPA at 40 PSI with 8,001 flat fan nozzles. Foliar application was made 21 Aug. Plots were sampled by visually counting the number of aphids on the underside of randomly selected sorghum leaves from the center rows of plots. Insect control was evaluated 24 Aug, 3 d after application (3 DAA), 28 Aug (7 DAA), and 3 Sep (13 DAA). Ten flag leaves and ten leaves in the lower half of the canopy were sampled 3 DAA, and eight leaves of each were sampled at 7 and 13 DAA. Aphid numbers from upper and lower leaves were averaged for the data presented. Yield data were collected 11 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 LSD.

All foliar insecticides except dimethoate reduced the average number of sugarcane aphids at the first two evaluation timings (3 and 7 DAA, Table 1 ). The high rate of Sivanto reduced aphid numbers more than Lorsban Advanced alone and the Lorsban Advanced + dimethoate tank mixture at 3 DAA. By 7 DAA, the high rate of Sivanto had fewer aphids than dimethoate, Lorsban Advanced, the Lorsban Advanced + dimethoate tank mixture, and the low rate of Transform. Both rates of Sivanto controlled aphids better than all other insecticide treatments at 13 DAA. Also at 13 DAA, the higher rate of Transform had fewer aphids than dimethoate, Lorsban Advanced, and the Lorsban Advanced + dimethoate tank mixture. There were significant differences in yield among treatments. Plots treated with either rate of Sivanto had the numerically highest and statistically similar yields. Plots treated with the low rate of Sivanto yielded more than those treated with dimethoate, Lorsban Advanced, the Lorsban Advanced + dimethoate tank mixture, both rates of Transform, and the nontreated check. The yields in plots treated with dimethoate or Lorsban Advanced + dimethoate were statistically similar to the nontreated check. No phytotoxicity was observed with any treatment. However, plants in nontreated plots and poor performing insecticide treatments were dead or dying as a result of aphid infestations by 21 DAA (data not shown).

Author notes