Who or what is eating your corn?

Al Lowe

Actually, there are quite a lot of different things which may be eating your corn besides you, your family, or your customers. Let’s take a brief look at some of them.
First, the Corn Earworm (Heliothis zea). The adult is a moth, fairly small, brownish to yellowish in colour. The adult eats only nectar from flowers, so it doesn’t do any damage to corn at all. It is the larval (caterpillar) stage which is the culprit. The eggs are laid in the early spring, and hatch out into one of the most destructive insects that corn has.
At first, these grubs feed on tender shoots and leaves. But the real damage is done to the ears. They are very fond of the tassels, and can do away with most of them on a corn ear in a very short time. After that they head into the kernels themselves, working from the top down toward the base. While they don’t usually destroy the whole ear, their progress makes the corn cob unfit for market. The caterpillar itself is a good size - maybe up to about two inches. It has several stripes, and may be brown or greenish. It not only eats corn, but is a serious pest on tomatoes, cotton and about a hundred other plants. In really serious infestations, there may be up to 4000 or more of these caterpillars on one acre of corn land.
Next, the European Corn Borer, (Ostrinia nubilalis). As its name suggests, it was not a native to this continent. It came on ships about eighty or so years ago.
The adult of this insect is another moth - a relatively unimpressive one of yellowy brown colour. The male moth is smaller and darker than the female, and has some rather dark bands on its wings. The larvae are sort of pinky, have brown spots along the sides, and a dark brown head. You have very likely seen them.
Again, eggs are laid in the spring. The little caterpillars burrow their way into the plants, and eventually find their way to the cobs. You can often find them right in the kernels.
The larvae pass the winter in the corn stubble, and corn scraps on the ground. It is important to do fall ploughing on your corn patch. As there are two generations of this pest, the early spring moths get at the early corn, and the summer moths the later crop.
Now that’s not all by any means. Grasshoppers eat corn, although only a really heavy infestation is a serious problem.
There are some species of Flea Beetles which also get into your corn. They are called that because when they are frightened, they jump like a real flea does. They also carry a bacterium which makes the corn rot.
One common old enemy the white grub, will also lunch on the roots of corn. It lives in the ground for three years, so it has lots of time to feed on your crop. It is the larva of the June Beetle.
And the Army Worm, the real one (not the Tent Caterpillar which is often misnamed) lives mainly on grass plants. Since the corn is just a great big grass plant, it is fair game.
But the corn farmer has some friends, too. There are bacterial, fungus and protozoan diseases which attack these insects. Other insects are parasitic on them. One wasp lays its eggs on as many as 30% of the caterpillars in the U.S. Corn Belt. Lady bugs will eat dozens of eggs in a day. Birds will eat both the moths and the larvae. One of the best controls is ‘clean’ farming. Fall or early spring ploughing, careful summer tilling, crop rotation, and so on. Talk to your Ag Rep. He can help you in your constant battle against our insect pests.