Midwest Vegetable Guide - 2022 - 274

Sweet Corn - Insects
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,
274
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: 0day.
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
Midwest Veg Guide 2022
Midwest Vegetable Guide - 2022

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