Year: 2024
Type: article
Abstract: Corn earworm (CEW) is the primary pest of sweet corn in the Mid-Atlantic region. Pyrethroid resistance is well documented, but there are few other effective modes of action available for CEW control in sweet corn. The purpose of this study was to evaluate the efficacy of foliar insecticide treatments on the control of CEW in sweet corn. Treatments were applied to ‘American Dream’ sweet corn planted on 17 Jun and 5 Jul 2022 at the University of Delaware Carvel Research Center, Georgetown, DE. Plots were 2 rows by 20 ft with a 1-row buffer between treatments. Treatments were replicated 4 times in a randomized complete block design. Insecticides were applied with a CO2-pressurized backpack sprayer with single-row boom directed to ear spray equipped with 2 D2 tips and #25 cores delivering 40 GPA at 38 PSI. All treatments, except the untreated check, received Induce (0.25% v/v). In the 17 June planting, treatments were initiated 2 days after the first silk. Treatments were initiated 4–5 days after the first silk in the 5 July planting. Treatments were applied at 3-day intervals, with 6 applications made between silking and harvest. Treatment efficacy was assessed from 25 random ears from each plot. The presence and location of corn earworm damage and the size of larvae present were recorded from each ear. The first planting was harvested on 22 August. The second planting was harvested on 6 September. All data were analyzed using ANOVA and Tukey–Kramer HSD means separation using JMP. All treatments from plots planted on 17 Jun had significantly fewer number of medium and large corn earworm larva than the untreated check (Table 1). Ears treated with Hero at 10.3 fl oz/acre had significantly fewer total CEW than ears treated with Warrior II. All treatments had a significantly higher percent of clean (fresh market) and processing ears than the untreated check. Hero at 10.3 fl oz/acre had a significantly higher percent of clean ears than Warrior II and Brigade. Means within columns followed by the same letter are not significantly different (P > 0.05, Tukey–Kramer HSD means separation). Treatment applications occurred on 3, 6, 9, 12, 15, and 18 Aug. aCEW instars 1−2. bCEW instars 3−4. cCEW instars 5−6. dPercent of ears with no CEW damage or larva present. ePercent of ears with no CEW damage or only a small amount of damage to the tip of the ear. The delay in treatment initiation in the 5 Jul planting contributed to a lower percentage of clean ears and greater variability in protection in treatments that historically provide better protection. All treatments from plots planted on 5 Jul had significantly fewer total CEW than the untreated check except for Brigade and Mustang Maxx (Table 2). Of the pyrethroids applied alone, only Baythroid XL had a significantly greater percentage of clean ears than the untreated check. The addition of Intrepid Edge improved upon Warrior II’s performance only at a high rate. Vantacor at its higher rate resulted in a greater percentage of clean ears than Mustang Maxx and similar to all of the other pyrethroids. Elevest rotated with Baythroid XL and the high rate of Intrepid Edge + Warrior II provided the best earworm control. Pyrethroids alone resulted in a significantly less percentage of processing ears with the exception of Mustang Maxx, although Mustang Max had a very low percentage of clean ears.1 Means within columns followed by the same letter are not significantly different (P > 0.05, Tukey–Kramer HSD means separation). Application A = 19 Aug, B = 22 Aug, C = 25 Aug, D = 28 Aug, E = 31 Aug, and F = 3 Sept. aCEW instars 1–2. bCEW instars 3–4. cCEW instars 5–6. dPercent of ears with no CEW damage or larva present. ePercent of ears with no CEW damage or only a small amount of damage to the tip of the ear. *Total meant Includes exits where a CEW completed development and worms which had died in the ear.
Source: Arthropod management tests
DOI: 10.1093/amt/tsae049
Authors: David Owens, Morgan Malone
Institution: University of Delaware
Language: English
Subfield: Insect Science
Domain: Life Sciences
SDG: Zero hunger
Open Access status: gold
Estimated APC paid: $300
OpenAlex ID: W4395699433