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Corn products with insect traits have the potential to improve grain quality and protect yield potential by providing multiple modes of action for advanced above-ground insect protection (Figure 1). VT Double PRO®, Genuity® VT Triple PRO®, and SmartStax® technologies provide dual modes of action for above-ground insects, including CEW. Other corn products containing insect protection traits such as Optimum® AcreMax® or Optimum® Intrasect® have no mode of action against CEW. Please visit www.genuity.com for applicable trait products and refuge requirements for the corn-growing and cotton-growing areas.
Corn earworm larvae feed on corn ears, cotton squares and bolls, grain sorghum seed heads, and soybean pods and seeds. When small, CEW larvae are pale yellow, while the larger larvae are pale green to dark brown. There are 3 to 4 stripes across their body length and numerous small, black spines along their back and sides (Figure 2). When disturbed, they curl into a C-shape.1
Similar Larvae. Larvae of CEW can be mistaken for fall armyworm (FAW), true armyworm (TAW), European corn borer (ECB), southwestern corn borer (SWCB), or western bean cutworm (WBC). However, they can be identified by markings and head capsule color:
There are usually two generations per year in much of the Midwest, but multiple generations can occur in the southern states per year. The adult moth (Figure 5) migrates from the southern states to other areas of the Corn Growing Area/Midwest with winds and storms in late spring and early summer.
First generation moths mate and females lay eggs in the whorl of the corn plant, while the second generation lays eggs on corn silks. Each female can produce 500 - 3,000 eggs.1
First generation CEW larvae feed in the whorl causing numerous ragged holes on the unfurled leaves and slight defoliation (Figure 6).
The second generation usually appears during pollination. Larvae enter the corn ear primarily through the silk channel.
Feeding may cause damage to the tassel, silks, and kernels.2 As silks dry, CEW begin feeding on tip kernels and along the sides of the ear near the tip. Injury from CEW larvae feeding can provide an entry point for secondary pests, including fungi, that may produce mycotoxins. Because CEW larvae are cannibalistic, only one larva typically survives per ear.
Early Feeding. Scouting for CEW should begin in early spring. Potential damage from CEW can be estimated by using pheromone traps to count adult moths that enter an area to lay eggs.
Late Feeding. Scouting for CEW larvae should also occur later in the season by evaluating corn ears. Although damage may have already occurred, products can perform differently in regards to CEW feeding.
Monitor CEW Feeding and Damage. It is highly recommended to follow the non-destructive steps, outlined below, to evaluate CEW damage, to keep the corn ear attached:
Comparing Larval Ear Feeding Damage.2
If the corn crop does not contain B.t. traits that offer control against CEW, an insecticide application may be considered in whorl stage corn, if economic threshold levels are met. Insecticide use for CEW feeding on corn ears is not economical because the CEW is protected by the ear husk.