Tomato Hornworms (Manduca quinquemaculata)
Tobacco Hornworms (Manduca sexta)
These related hornworms can devastate your tomato plants before you know that you have a problem.
The plant in the foreground of this photo used to be a thriving tomato plant with leaves and tomatoes Overnight, the hornworms will consume all of the leaves of the plant, and, if they are still hungry they will go to work on the tomatoes themselves.
These green caterpillars are the larvae of the large and beautiful (ok, maybe not) sphinx moth. They are both about 3-4 inches long and have a horn which cannot sting projecting from the rear. The tobacco hornworm (Manduca sexta), shown here, has seven white diagonal stripes on each side. The horn is curved and is red. The cousin, the tomato hornworm (Manduca quinquemaculata), has eight white V-shaped markings on each side. Its horn is black and straight.
The hornworm (and, of course, the sphinx moth) occur throughout North America. In the north they produce one generation a year and in the south can produce two or more. The pupae of the hornworm can overwinter in the soil.
Besides tomatoes, they also are attracted to angel trumpet, dill, eggplant, nicotiana, pepper, petunia, potato, and tobacco.
There is a parasitic wasp that lays small white cocoons on the back of the hornworm. If you see this, and capture the hornworm you can watch the wasp kill the hornworm and emerge as a wasp. Let it go to kill more hornworms.
Other natural predators are the praying mantis, assassin bugs, many species of birds, moles, and some toads.
If you cannot wait for this natural process the best method of control is to hand pick the hornworms when you see them. You can also use Bacillus thuringiensis (BT) spray, or if you have a bad infestation you can use a pyrethrum spray.
Emily: Have you ever seen a tomato worm at work? It's scary!
(A north Florida gardener)
A: Rodale's Garden Problem Solver says that the best control strategy is to hand pick them early. They say you can also us Bacillus thuringiensis (BT) spray, or if the infestation gets out of hand, a pyrethrum spray. Hand pick is best. Then eat them with a little olive oil.