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Tomato hornworms invade gardens in Carbon County

Carbon USU Extension agent

Tomatoes are starting to ripen in the Castle Country region.

Tomato hornworms have been found in large quantities in some local gardens.

Tomato hornworms are a caterpillar that can grow up to four inches long - as long as a man's index finger.

They are the larval stage of the sphinx moth, also called the hummingbird moth.

As they get older they can defoliate a tomato plant and even eat green tomatoes.

The green color and stripes on their sides make it hard to see them in spite of the large size.

The easiest way to find the worms is to look for the frass or insect feces below the plant.

People should then scout for the offending caterpillar in the leaves.

The worms will usually be grasping along the bottom of a leaf vein so it helps to get low and look up.

Early morning or late evening when the sun angle is low is a good time to look for the insects.

Once the caterpillars have been removed from the plant they should be disposed of quickly.

Chickens love the worms.

There are parasitic wasps that will lay eggs on tomato hornworms.

Parasitized hornworms are easy to recognize as they will have small white extensions from the body.

Parasitized hornworms should be left alive as that will encourage the survival of the parasitic wasps.

If Carbon County gardeners are afraid they are not able to find and destroy all the insects, they can spray tomatoes with a Bt product that is labeled for hornworms.

Control products that contain Bt are safe and tomatoes can typically be harvested shortly after spraying.

Local residents should be sure to read and follow label directions.

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