Plant Disease Symptoms: What Are Corn Earworms?

Striped earworms feeding on your corn? Could be heliothis zea. Find out more.

What is it?

Heliothis zea, or corn earworms are striped worms which feed on corn as well as many other flowers and garden vegetables. In addition to being known as corn earworms, they are also known as cotton bollworms and tomato fruitworms.

What does it look like?

Heliothis zea has distinctive stripes which can be yellow, green or brown and they can range anywhere in size from 1/4 inch to 2 inches in length. Damage from corn earwroms will show up as leaves that are chewed or frayed looking or tips of corn which appear damaged. The corn earworm feeds on the tip of the ear of corn inside the husk as well as the leaves it has to chew to get to the ear itself.

How does it manifest?

Corn earworms are the larvae of moths. The adult moths tend to be greyish-brown and have darker brown distinct lines on their wings. Each spring, adult female moths lay eggs on the undersides of corn leaves as well as within the corn silks. Typically only single eggs are laid within the silk. When the earworm larvae hatch from the eggs, they feed on nearby leaves and their feeding can stunt the overall growth of the crop. However, the worst case of earworms is one where the worms have fed on the silks which can result in poor pollination and interrupted kernel development. Corn earworms can produce several generations within a growing season.



What can you do about it?

In order to use insecticides effectively, you need to treat the corn earworms before they bore into the ears. Dusting the garden with carbaryl can be an effective treatment. If you repeat the application at intervals of three days for three or four applications you should effectively control the earworms. However, if reinfestation occurs you can safely treat the corn at intervals of three days right up until the time of harvest if necessary.

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