Figure 1. Larva feeding on kernels
The corn earworm, Helicoverpa zea (Boddie),
is the most serious insect pest of sweet corn in
Tennessee. This pest feeds directly on the market
Early in the season, corn earworm larvae feed
on the foliage of seedlings in the whorls. As the
blades unfurl, ragged holes are seen in the leaves.
Light brown excrement becomes lodged on the
leaf blades and in the whorl. This type of damage
is known as “shatterworm” injury.
Corn earworms prefer the fruiting stages
(ears) of corn. Therefore, as the plant develops
fruit, larvae move to those plant parts. Damage
results from larvae feeding on the kernels in the
ear tip area (Figure 1). Round emergence holes
(approximately 3/16 inch in diameter) in the shuck
are often mistaken for entrance holes.
Description and Life Cycle
Corn earworms overwinter as diapausing pupae
in the soil, usually at depths of 2 to 4 inches (Figure
2). Adult moths begin to emerge in early May.
Wings on adult female moths have a span of about
1½ inches and are yellowish brown with darker
lines and spots near the tip of the wings (Figure 3).
There is a conspicuous, dark, comma-shaped spot
Corn Earworm on Sweet Corn
Frank A. Hale, Professor
Originally developed by Jaime Yanes, Jr., former Assistant Professor,
and Harry Williams, Professor Emeritus
Entomology and Plant Pathology
on the front wing. The moths’ eyes are greenish.
Moths are most active at night. After mating,
female moths seek the leaves of seedling corn for
egg laying early in the season. However, once the
corn begins to silk, most of the eggs are laid singly
on the silks.
Each female may lay from 450 to 3000 eggs.
Eggs are 1/32-inch in diameter. When fi rst laid, eggs
are pale white. Prior to hatching, a pale reddish
band forms; then the egg darkens. Eggs hatch in
two to fi ve days and newly hatched larvae crawl
down into the tip of the developing ear to begin
feeding. Larvae develop through fi ve or six instars
(the larval stages between su