by Dave Molinaro
If you see a large green worm with a stinger on its tail and a series of eight diagonal white lines that join to form V’s along both sides of its body crawling along the branch on your tomato plant; if you notice round holes with rough edges on your tomato leaves, large fecal pellets or entire leaves stripped; you may have the tomato hornworm or its cousin the tobacco hornworm.
The correct term for the so-called stinger is an (excuse the expression) anal horn. They cannot sting you.
The tobacco hornworm has a red anal horn, while the tomato hornworm has a black one. The worms are usually green, but can be a reddish brown. Many will grow to at least three inches in length. They feed mostly on leaves and occasionally fruit.
Hand removal is the quickest way to get rid of them. On the other hand, if your plants are infested with hornworms, you can control them with an insecticidal soap known as Bacillus thuriengensis, sold under several trade names, including Dipel, Biotrol and Thuricide.
The tomato hornworm does have a natural enemy, the braconid wasp. If you see little white sacs on your hornworm—like the one pictured right—you know braconid wasps have laid their eggs on it. When the eggs hatch they burrow into the worm and use it as a food source. These wasps are not harmful to us. Do not destroy or remove this infected hornworm from the garden. At this stage the worm is no longer capable of causing damage to your plants. Let these wasps complete their life cycle so they can hunt down more hornworms.
Dave Molinaro, is a former Extension Master Gardener Volunteer with Mecklenburg County, NC. During his tenure as an active volunteer, Dave was a frequent—and witty—writer for the in-house newsletter, The Thymes.
Got GARDEN questions? Get answers!
The more you know, the more you can grow.
growing & gardening in the Southeast
Mecklenburg Extension Master Gardener Volunteers