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Sweet Corn - Insect Identification and Control in the Home Garden

A statewide monitoring network gives flight catches of European corn borer, corn earworm, and fall armyworm. Data are contained in the Vegetable Insect Newsletter on the PENpages system. Contact your county extension office for more information. Call 1-800-PENN-IPM for flight data.

Corn Earworms

Earworms are large (up to 1 3/4 inches) and vary greatly in color, from a light green or pink to brown with alternating light and dark stripes running lengthwise on the body. The worms are a minor problem on early and mid-season corn, but after August 15 and especially on corn that silks in September, the crop often is heavily infested. Spray the ear zone when plants are 30 percent, 50 percent, and 100 percent in silk. Corn harvested in late September may need five sprays.

Control : Brushing silks with horticultural oils during heavy flights of adults (August 15-September 15) may help if done several times as the silks grow. Cutting tips off ears removes worms. Consult the most recent Commercial Vegetable Production Guide  (available at your County Extension Office) for specific control measures. Follow directions on the labels according to plant type when applying insecticides.

European Corn Borers

Borers are up to 1 inch long, flesh-colored, and marked with numerous small, round, brown spots. They feed in all parts of the stem and ear. A group of small pinholes on the leaves is characteristic of borer feeding. If over 30 percent of the plants have feeding injury, several sprays are suggested. The best time to control the first brood with sprays is during the last two weeks of June. To control the second brood, apply sprays during August.

Control : Consult the most recent Commercial Vegetable Production Guide  (available at your County Extension Office) for specific control measures. Follow directions on the labels according to plant type when applying insecticides.

Fall Armyworm

Fully grown larvae are about 1 1/2 inches long; worm colors vary from light tan or green to black with a black stripe along each side. The head has a prominent "y" with a series of dark spots running along the back, and the last or next-to-last abdominal segment has four distinct black dots.

Control : Consult the most recent Commercial Vegetable Production Guide (available at your County Extension Office) for specific control measures. Follow directions on the labels according to plant type when applying insecticides.

Sap Beetles

These beetles can be found feeding on silks from June through August, but particularly during July. Dusky sap beetles are small, about 3/16 inch long. They are gray to black in color and oblong in shape. They invade plants when tassels begin to show, feed on green silks, and feed on kernels when the silks begin to brown. Damage from corn borer larvae and Japanese beetles attract sap beetles.

Control : Consult the most recent Commercial Vegetable Production Guide (available at your County Extension Office) for specific control measures. Follow directions on the labels according to plant type when applying insecticides.

Flea Beetles

Flea beetles are small (1/16 inch) and black, and can be recognized by their jumping habit when disturbed. They eat the surface from the leaf, causing a white streak parallel with the veins. Flea beetles are most abundant in warmer areas of the state and especially after mild winters. The beetles are most important in their transmission of a disease known as Stewart's wilt or bacterial wilt.

Control : Where wilt has been a problem, grow resistant varieties. If necessary, Consult the most recent Commercial Vegetable Production Guide (available at your County Extension Office) for specific control measures. Follow directions on the labels according to plant type when applying insecticides.

Warning

Pesticides are poisonous. Read and follow directions and safety precautions on labels. Handle carefully and store in original labeled containers out of the reach of children, pets, and livestock. Dispose of empty containers right away, in a safe manner and place. Do not contaminate forage, streams, or ponds.

Authored by: Shelby Fleischer

February 2000

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