Impact of various insecticides on cotton aphid infestation in the Texas Blackland Prairie, 2024

A field evaluation of insecticides targeting aphids infesting cotton was conducted in Hill County, Texas, United States. The Phytogen (Corteva Agriscience) cultivar “PHY 490 W3FE” was utilized for this test. Aphid populations over the course of this test were concentrated on the terminal and upper third of the crop canopy. At the start of the trial on 28 June 2024 the crop was at the first bloom stage, and aphid populations exceeded the local recommended economic threshold of 40 aphids per leaf. The selected insecticides (Table 1) were replicated four times in a RCB design, with 10 feet (4 rows) by 40 feet long plots. Treatments were applied as a foliar broadcast spray utilizing a CO₂ backpack sprayer calibrated to apply 13.6 gal. acre^-1. Aphid populations were estimated at 0, 3, 6, 9, 13, and 20 DAT on 10 random leaves from the upper third of the canopy per plot on the center 2 rows. Lint yield was collected by hand harvesting 10 linear row feet from the center 2 rows, and then ginned using a 10-saw tabletop gin. Aphid densities were Log₁₀(x + 1) transformed due to the 0, 3, 6, 13, and 20 DAT not meeting the assumption of ANOVA, but the untransformed means are presented. All data was subjected to ANOVA procedures with means separated using Fisher’s F-Protected LSD (P = 0.05).

Aphid populations at the start of the trial ranged from 37.1 per leaf for Centric at 2 oz acre^-1 to a high of 73.28 aphids per leaf for Sefina at 3 fl oz acre^-1. Statistical differences were observed between treatments at 3 DAT with Transform WG averaging 2.2 aphid per leaf and the untreated check averaging 84.9 aphid per leaf (Table 1). By 6 DAT all insecticide treatments except for PQZ were significantly lower than the untreated check, and reduced aphid densities below the economic threshold. At 10 and 13 DAT aphid densities in all insecticide treatments were statistically lower than the untreated check. At 20 DAT statistical differences were not observed among treatments, but all insecticides had aphid populations below the local economic threshold of 40 aphids per leaf. Statistical differences were observed among treatments for pounds of lint per acre and ranged from 452.1 lbs. lint acre^-1 for Sefina to a high of 724.6 lbs. lint acre^-1 (Table 1). Based on these results Transform 50WG and Intruder Maxx can provide quick knock down of aphid populations, but all insecticide tested except for PQZ and Centric 40WG can provide significant control of aphid populations in cotton. The excellent control provided by Macho 4.0 in this trial is likely a result of the aphid population being concentrated to the upper third of the crop canopy.¹

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