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Corn Earworm Pest of Sweet Corn

Corn Earworm Pest of Sweet Corn

FS221E
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Timothy Waters, Regional Vegetable Specialist, Washington State University, Franklin and Benton County Extension, Carrie Wohleb, Regional Vegetable Specialist, Washington State University, Grant-Adams County Extension
In the US, sweet corn’s most destructive insect pest is the corn earworm. With the goal of aiding commercial producers and crop consultants, this publication describes the biology of corn earworms and the damage they cause to sweet corn as well as scouting techniques and control options for managing this pest.
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The corn earworm (Helicoverpa zea) is the most destructive insect pest of sweet corn in the US and has been noted to be one of the most destructive plant feeding insects in the world. Preferred crops for earworm include corn, tomato, sorghum, vetch, and cotton (McMillan et al. 1966). On these crops, the pests are called corn earworm, tomato fruitworms, sorghum headworm, vetchworm, and the American cotton bollworm, respectively. Corn earworm will also feed on numerous other crops, including alfalfa, oat, soybean, sunflower, asparagus, cabbage, cantaloupe, cucumber, eggplant, bean, pea, pepper, potato, pumpkin, and watermelon as well as some weed hosts (Martin et al. 1976). Corn earworm occurs throughout the Americas, being a native insect pest occurring from Argentina in the south to Canada in the north (IIE 1993). The goal of this publication is to discuss the biology of corn earworm and to aid commercial producers and crop consultants by providing scouting techniques and control options for this pest in sweet corn.

Description and Biology

The complete life cycle of the corn earworm consists of egg, larva, pupa, and adult. Adults are light to dark brown, or light olive green moths with a wing span of about 1 1/2 inches (Figure 1). The wing color pattern of the earworm moth can be highly variable. Eggs are about half as large as a common pinhead, globular, and vary from light yellowish green to dusky brown. Newly hatched larvae are yellowish white with black heads. Larvae, when full grown, are about 1 1/2 inches long with conspicuous cream, yellow, brown, slate, or black stripes on pink, green, cream, or yellow backgrounds (Figure 2). The pupae, or resting stage, are reddish brown and about one­inch long.

Figure 1. Corn earworm adult moths (left); false corn earworm adult moths (right).

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