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Staving off worms from summer corn

POSTED: July 4, 2014 1:00 a.m.

Sweet corn in the summertime is probably everyone’s favorite home garden vegetable. But do not let your hard efforts of growing it go to waste by ending up with wormy corn.

The two major worm pests of early sweet corn are the corn earworm and the European corn borer.

The corn earworm varies from light green to pink to brown with alternating stripes running lengthwise on the body. The head is unusually yellow. A fully grown worm is up to 1 3/4 inches long.

The European corn borer is flesh colored with rows of round doughnut-like rings along the body and brown head. When fully grown, the body is about 1 inch long.

Both pests begin by feeding on the whorl of the plant. However, the habits of the two worms differ after the early feeding.

The European corn borer will burrow into the stalk. This will weaken the stalk and reduce the yield. The stalk also may fall over if many worms are feeding.

Unlike the borer, the corn earworm makes a beeline for the ear as soon as the corn begins to silk. The earworm enters the tip of the ear and feeds on the end. The earworm loves the kernels far more than the leaves.

Adult moths likewise no longer lay their eggs in the whorl, but aim for the silk.

The European corn borer likewise heads for the ear, but it enters from the stalk, the side of the ear or the silk.

It is almost impossible to grow sweet corn without the corn earworm sharing it with you. Large ragged holes in the leaves, sawdust castings and broken tassels are evidence the worms have found your corn patch.

However, two things can be said in the earworms’ favor.

One, they do not like each other. If two worms are in the ear, one will eat the other. That is why you rarely find more than one live corn earworm in an ear.

Two, they tend to only stay at the tip end. By chopping off the damaged end, the ear is still edible.

The European corn borer has no such redeeming qualities, but fortunately it is not as common.

Corn borers will be found in groups and will chew their way up and down the length of the ear.

So what to do? Use products containing B.t. (Bacillus thuringiensis) and spray it on the leaves and silks of the plants. As the worms feed, they will ingest the bacterium which disrupts the digestive system.

This is the least toxic method of treatment you can use. Mixing B.t. with mineral oil improves the control.

Other chemicals available to use are carbaryl, cyhalothrin, cyfluthrin, permethrin or bifenthrin.

There is nothing better from the garden than fresh sweet corn, but these two worms love it, too. Apply some control if you do not want to share too much of it.

Michael Wheeler is county extension coordinator for the UGA Cooperative Extension office in Hall County. Contact him at 770-535-8293, www.hallcounty.org/extension. His column appears on gainesvilletimes.com/life.


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