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2022 Midwest Vegetable Guide

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Sweet Corn – Insects 274 Midwest Veg Guide 2022 Caterpillars All moths can be monitored with pheromone traps. When moths are being caught in traps, it means they are mating and laying eggs in the crop. European corn borer (ECB) eggs are laid on leaves, usually on the undersides, in the region of the ear. Larvae feed on the leaves and later may migrate to the ears (if present). Corn borers can be controlled by spraying during the late whorl, tasseling, and silking stages. The migrating larvae should contact a lethal dose of insecticide while moving to the ear zone. Western bean cutworm (WBC) eggs are laid on the top surface of leaves on corn that is in pre-tassel. They have one generation per year from mid-July to early August. Sweet corn that has well-developed ears during flight is less likely to be infested; however, tillers (suckers) that have not tasseled may be attractive for egglaying. Corn earworm (CEW) eggs are laid directly on green silks. The larvae that hatch from those eggs will follow the silks down into the tips of the ears. Corn earworms must be controlled by directing sprays at the silks, such as using drop nozzles, so larvae will immediately contact the insecticide after hatching, prior to being protected once they enter the ear. Fall armyworm (FAW) eggs are laid on corn leaves, and newly emerged larvae consume large quantities of foliage as they rapidly grow. FAW will feed on all stages and parts of the plant, but the pre-tassel whorl is preferred. Caterpillars can directly penetrate husks and damage ears. These caterpillars are likely to co-occur in a sweet corn field during some parts of the year. Do not treat separately for European corn borer and corn earworm. ECB: treatment is justified when more than 10 moths per night are caught in traps while corn is in late whorl stage or when 20 percent or more of the plants show larval feeding. One application during the late whorl stage, followed by additional treatments every five days up until seven days of harvest, usually provides adequate control. WBC: treatment is justified when moths are being caught in pheromone traps or larval damage is present when corn is in late whorl stage. CEW: treatment is justified when moths are being caught in traps while green silks are present. In general, the higher the moth catches, the shorter the interval between sprays. If fewer than 5 moths are being caught per night, a five-day spray interval should be adequate. As moth catches approach 50 to 100 per night, a two- to three-day spray interval would be more appropriate. If no field corn in the area is silking, moths will lay eggs primarily on silking sweet corn. In this situation, use a threshold of 1-3 moths per trap per night. Stop treating for corn earworms when 90 percent of the silks are brown. FAW: treatment is justified when moths are being caught in pheromone traps or larval damage is present when corn is in late whorl stage. Pesticide Asana XL (0.66EC) (esfenvalerate) | 2.9-9.6 fl. oz. per acre. Caterpillars include cutworms, corn borers, and earworms. Do not exceed 9.6 fl. oz. per acre per season. REI: 12-hour. PHI: 1-day. IRAC 03A. RUP. Baythroid XL (1EC) (beta-cyfluthrin) | 0.8-2.8 fl. oz. per acre. For armyworms, corn borers, cutworms, and earworms. See label for pest-specific rate recommendations. Do not exceed 28 fl. oz. per acre per season. REI: 12-hour. PHI: 0- day. IRAC 03A. RUP. Besiege (ZC) (chlorantraniliprole, lambda-cyhalothrin) | 6-10 fl. oz. per acre. For armyworms, corn borers, cutworms, and earworms. Do not exceed 31 fl. oz. per acre per season. REI: 24-hour. PHI: 1-day. IRAC 28, IRAC 03A. RUP. Brigade 2EC (bifenthrin) | For armyworms, and cutworms use 2EC formulations at 0.3 fl. oz. per 1,000 linear ft. of row in a minimum of 3 gals. of finished spray as a 5- to 7-inch band over an open seed furrow (T-band) and do not exceed 6.4 fl. oz. per acre per season at plant application. For armyworms, corn borers, cutworms, and earworms, use 2EC formulations as a foliar application at 2.1-6.4 fl. oz. per acre and do not exceed 12.8 fl. oz. per acre per season (including any soil applications). Do not use 10DF, 10WP, or 10WSB formulations; they are not labeled for sweet corn. Allow 7 days between applications. REI: 12-hour. PHI: 30-day for soil applications, 1-day for foliar applications. IRAC 03A. RUP. Bt (Bacillus thuringiensis) products for caterpillars (Bacillus thuringiensis aizawai strain ABTS-1857, Bacillus thuringiensis aizawai strain GC-91, Bacillus thuringiensis kurstaki strain ABTS-351, Bacillus thuringiensis kurstaki strain EVB-113-19, Bacillus thuringiensis kurstaki strain SA-11) | REI: 4-hour. IRAC 11A. Bt (Bacillus thuringiensis) varieties (Cry1Ab, Cry2Ab, Cry1A.105, Vip3A) | There are four Bt proteins bred into sweet corn for control of armyworms, corn borers, earworms, and cutworms. Cry1Ab is effective on European corn borer but has never been effective on western bean cutworm. It is moderately effective on fall armyworm and corn earworm. Field corn with this single trait is not marketed for control of corn earworm or fall armyworm, but sweet corn still is. To slow down counter-resistance in pest populations the field corn market is moving away from single-trait varieties. Syngenta Attribute I Series sweet corn has this trait. Cry2Ab2 is always paired with Cry1A.105 and is effective on

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