CORN EARWORM 
( Heliothis armigera (Hbn.)) 
Life History 
Although the corn earworm attacks many cultivated crops, it is 
dealt with here only as an enemy of corn. The eggs are laid by a 
moth, or miller, usually on the corn silks. The eggs hatch in from 2 to 
8 days, and the tiny larvae, caterpillars, or “worms/’ feed downward, 
following the silks into the ear tip. Serious damage to the ear fre- 
quently results from their feeding and from the fermentation or molds 
which follow. When full-grown, the larva leaves the ear, enters the 
soil, and becomes a pupa, and from this the moth emerges. About 30 
days are required in midsummer for complete development from egg to 
adult. Pupae produced late in the summer or in the fall may pass the 
winter in the soil and become moths the following spring or early in 
the summer. Usually two complete generations are developed annu- 
ally in the North, but in the South there may be as many as five or 
more generations. 
Control 
Injury to field corn can be reduced by growing varieties having long, 
tight husks, and, in the South, by planting early. 
To protect early-market or home-garden sweet corn, inject into the 
tip of each ear about }{ teaspoonful (% to 1 cubic centimeter) of refined 
white mineral oil (viscosity 100 to 200 Saybolt) containing 0.2 percent 
of pyrethrins. If ready-mixed material is not obtainable, use 1% fluid 
ounces of oleoresin of pyretlirum (containing 20 percent of pyrethrins) 
to 1 gallon of the white oil. The injecting should be done after the 
silks have wilted and before they have begun to turn brown. If it is 
done before the silks have wilted, poorly filled ears may result. Al- 
though the mixture can be applied with a pump-type, long-spouted oil 
can, it can be best applied by using a special oiler. A description (with 
illustrations) of the special oiler will be sent, without charge, on applica- 
tion to the Bureau of Entomology and Plant Quarantine, United States 
Department of Agriculture, Washington, D. C. 
16—20761 
April 1941 
U. S. Government Printing Office 
For sale by the Superintendent of Documents, Washington, D. C. — Price 5 cents 
