AUGUST
1996

 

 

 

By
Tom Turpin
 
Professor of
Entomology
Purdue University

 

 

 

 

 

8-08-96

Worms Like Corn, Too

Corn! There is no food that is any more American, even apple pie. Corn, or maize as it is known worldwide, originated in North America, and for centuries, was a staple food for Native Americans. Today we still eat lots of corn as meal, in breakfast cereal, or whole kernels out of the can.

To many people the best way to eat corn is directly off the cob. Corn on the cob, or roasting ears as they are sometimes known, is one of the traditional foods of summer in the Midwest. Cookouts, county and state fairs wouldn't be quite the same without corn on the cob roasted over a charcoal fire.

Almost as much of a tradition as eating corn on the cob is removing the shuck from the ear and finding a worm feasting on the kernels. Yes, insects like sweet corn, too! And one of the insects with a taste for sweet corn has a name that reflects its propensity for showing up on corn ears. It's called the corn earworm. This insect, known scientifically as Heliothis zea, is one of the worst insect pests of corn. It is an insect that is found around the world and is a very general feeder. For instance, it also is known as the tobacco budworm, the tomato fruitworm, the cotton bollworm and the vetchworm because it feeds on those plants as well as many others.

So how does the worm get into the end of the sweet corn ear? In the adult stage, the earworm is a moth. The female moth flies about looking for good food plants for her offspring. When she finds such a food, like the silk on the ear of corn, she deposits an egg — something she might do 1,000 times in her lifetime. The egg hatches and the worm begins feeding on silks. Eventually the worm works its way into the ear tip, where it consumes the developing kernels.

Earworms grow quickly, so they are nearly full grown — about 2 inches long — when the corn is ready for human consumption. Earworms not only eat the kernels down to the cob, they add insult to injury by leaving a mess behind. Yes, corn tissue run through the digestive system of an earworm is left on the ear as a moist, yellowish-brown mass.

Most people don't like to find worms sharing their summer feast of sweet corn, so producers try to limit the number of earworms by treating the corn plants with insecticide when needed. The worms generally feed only in the ear tip, so many people remove the worm and its damage by breaking off the tip before plopping the ear into a pot of boiling water.

One thing about earworms in corn is that there is seldom more than one per ear. These worms are such voracious eaters that when they encounter another worm on an ear, one of them gets devoured. That's the way it is with eating corn on the cob, most people don't want to share with someone else!

 

Writer: Tom Turpin
Editor: Andrea McCann