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Corn Earworm


Common Names: Corn Earworm, Tomato Fruitworm, Cotton Bollworm, Sorghum Headworm

Scientific Name: Order Lepidoptera, family Noctuidae, Heliothis zea or Helicoverpa zea

Size: Adult wingspan--1 1/2", larva--3/4" to 1 1/8"

Identification: Adult moths are greenish gray or brown with black markings on the forewings. Larvae vary greatly from green to white to red to dark gray. Eggs are yellow or light brown, spherical domed, ridged, usually laid singly on host plants.

Biology and Life Cycle: Night flying, up to seven generations per year. Larvae have five or six molts, grow to maturity in a few weeks, then crawl into the ground, burrow to 6 inches, and pupate. Adult emerges in two or three weeks at night and finds a sheltered place to expand and dry its wings. Adults mate, live about two weeks; females deposit up to 3,000 eggs. About three generations a year. The last pupal stage overwinters. Pupae overwinter in the soil.

Habitat: Beans, corn, peas, peppers, potatoes, squash, tomatoes--even roses and cotton.

Feeding Habits: Larvae eat the foliage and buds of many crops such as tomatoes, beans, cotton bolls, lettuce crowns. They enter the corn ears at the tip, eat the kernels at the end, and leave masses of moist castings that cause mold to form. They enter the stem end of tomatoes. Called tomato fruitworm when eating tomatoes. The larvae are cannibalistic if they run into one of their own.

Economic Importance: A cosmetic problem for home gardeners. Not seriously damaging to corn crops, but considered one of the most destructive pests to other agricultural crops.

Natural Control: Tachinid flies, trichogramma wasps, and naturally occurring Bacillus thuringiensis. Bats, birds, and other insectivorous animals.

Organic Control: Bt products for serious infestations. A drop of mineral oil on top of each ear after silks have wilted (sounds like too much trouble to us). Apply beneficial nematodes to the soil. Organic, healthy corn plants are bothered less, and early plantings are damaged less than late plantings.

Insight: It's good to find one of these worms in the end of the corn ear. It's a sign that the corn is fresh and uncontaminated with poison pesticides. They rarely eat more than just the tip anyway. Corn earworm moths have been intensively studied. They fly high and far to find food and have been detected at 10,000 feet. Bats have been found feeding on them at 3,000 feet. Dr. Phil Callahan did much of his studies for his book Turning into Nature using the corn earworm. Cotton farmers have learned to spray a natural, nontoxic garlic oil on their cotton during certain stages of plant growth. The garlic changes the taste of the cotton, causing boll worm to stop feeding and starve. A big cotton farmer we know uses garlic as his only pesticide. He mists the crops with the garlic solution the first time as soon as the plants have six leaves and then again every ten days until the cotton has a full canopy. This gives a four- to six-week residual after the last misting. He found it is best to spray late in the evening and at night, as you should any foliar spray. This natural program can work to control many plant-eating troublesome pests.

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