Fending off the hornworm

Have you ever gone out to your tomato patch in the morning to find a plant that consists only of stalk and leaf veins?

If you have, then you are probably familiar with tomato hornworm. This voracious caterpillar can devour all the foliage on a tomato plant, plus the tomatoes, in just one night.

Tomato hornworm (Manduca quinquemaculata) is the larvae of the sphinx or hawk moth. Many people also refer to this gray adult moth that has a wingspan of up to 5 inches as the hummingbird moth.

The adult moth lays solitary, pearl-like eggs on young tomato plant leaves. When the eggs hatch, the small larvae begin to feed. The larvae have a 1-inch-long horn on their tail, are usually green and have horizontal, white, v-shaped markings on each side of the body. Their color and markings make them almost invisible on a tomato plant.

Because of their large food intake, the tomato hornworm grows very rapidly. At full size they are often the diameter of your thumb and up to 3 or 4 inches long.

When the caterpillar matures, it crawls down the tomato plant, burrows into the soil and pupates. A few weeks later, the adult moth emerges and the second generation of hornworms gets to work.

At the end of the season, the second generation of larvae burrows into the soil about 4 to 6 inches deep and forms a casing in which pupation occurs. Pupae overwinter in these casings. Adults emerge in late spring the following year, and the life cycle begins again.

Hornworms are often hard to see because of their camouflaged markings. If you see droppings below a tomato plant that are about two times the size of a BB, or if you see tomato branches stripped with no foliage, begin looking for tomato hornworms.

If you find hornworms on your tomato plants, pick them off and dust your tomato plants with Sevin or dipel dust; or spray them with liquid Sevin, Thuricide or permethrin. If you have had these pests in the past, I recommend dusting your plants in June with sevin or dipel dust. Both pesticides are relatively safe in a vegetable garden and may keep you from losing a tomato plant or two.

By the way, if you do find some large tomato hornworms in your garden, you may want to keep them and go fishing. I hear they make great catfish bait. Happy fishing, oops, gardening!

Send your gardening and landscape questions to Paul Schnare at P.O. Box 699, Cape Girardeau, Mo. 63702-0699 or by e-mail to news@semissourian.com.