University of Illinois Extension

University of Illinois Extension

Hort Answers

Insect Damage

Corn Earworm
Helicoverpa zea

Corn Earworm in silk end of sweet corn.  Nixon
Corn Earworm in silk end of sweet corn. Nixon
5 (1 = rare 5 = annual)
3 (1 = very little damage 5 = plants killed)
Sweet corn and tomato

Plants Affected

The caterpillar is broadly striped; up to 1 inch long; and yellow, green, or brownish. The adult moth is yellowish, with brown markings and a 1-1/2 inch wingspan.

The caterpillar feeds on the tip of sweet corn ears, leaving a mass of brown fecal matter. As the tomato fruitworm, the caterpillar bores through tomato fruits, exiting through a hole 1/4 inch in diameter.

Life Cycle
There are several generations per year. In some portions of the state, the insect overwinters as a pupa in the soil. Adults also migrate into Illinois from the south on summer storm fronts. Yellowish eggs are laid singly on green corn silks and tomato leaves.

Use pheromone-baited cone traps to monitor for the presence of moths. For fresh-market sweet corn, if traps are capturing corn earworm moths, treat at two- to five-day intervals, from first silk until 90 percent or more of the silks are brown. For processing corn, if pheromone traps are catching more than ten moths per trap per night, treat at three- to six-day intervals, from first silk until 90 percent of the silks are brown. Treat to control tomato fruitworm when tomatoes are fruiting and pheromone traps capture twenty or more moths per night. Treatment may be delayed if no eggs are present on the leaves. Moths deposit few eggs in tomatoes if nearby corn is silking.

Related Resources
Home, Yard & Garden Pest Guide
U of IL - Distance Diagnosis through Digital Imaging
U of IL - Plant Clinic