Efficacy of Selected Insecticides for Managing Aphids in Cotton, 2019

A field trial was conducted to assess the efficacy of selected insecticides for managing cotton aphid, Aphis gossypii Glover, in nonirrigated cotton crop at the Revels Farms near Everetts, NC. The field was planted with ‘Stoneville 5020GLT’ cotton on 5 May 2019 at a seeding rate of 50,000 seeds/acre. Individual plots were 4 rows by 30 ft long with a 36-inch spacing between row centers. The plots were arranged in an RCB design with 17 treatments including an untreated check (Table 1), and treatments were replicated four times. The plots received insecticide treatments on 18 Jul 2019. Insecticide treatments were carried out using a pressurized backpack and a spray boom, fitted with TeeJet TX-10 cone spray tips spaced 36 inches apart delivering 10 GPA carrier volume at 40 psi pressure above the canopy. Post treatment aphid counts were taken on 22 Jul, 25 Jul, and 1 Aug; 4, 7, and 14 DAT, respectively. To estimate the cotton aphid density, the fifth leaf from the plant top were sampled from 10 random plants per plot and total aphid counts were noted. To normalize the data distribution, A. gossypii counts from 4 DAT were square-root (x + 1) transformed, and 7 and 14 DAT were log₁₀(x + 1) transformed before analysis. Data were analyzed using ANOVA (PROC MIXED, SAS v. 9.4), and mean separations were carried out using Fisher’s LSD (P ≤ 0.05). Untransformed means are presented (Table 1).

At 4 DAT, all insecticide treatments, except for Brigade, Bidrin, Fulfill, Admire Pro, and Exirel, significantly reduced aphid density on cotton compared with the untreated check (Table 1). At 7 DAT, seven insecticide treatments significantly lowered the aphid population compared with the untreated check (Table 1), and Carbine and Sefina resulted in the lowest density of cotton aphids in the plots. Treatments did not yield significant differences at 14 DAT (P = 0.6067), and therefore results were not presented in Table 1.¹

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