Hornworms typically grow 3 to 4 inches in long. One species has a red horn; another has a black horn. Both like tomatoes and their relatives. - Photo: Robert L. Anderson, USDS Forest Service, www.insectimages.org

This a young tomato shows typical hornworm damage: stems stripped leafless.

Hornworms carrying around little white cocoons have been parasitized by a tiny natural enemy, a braconid wasp. Leave them in place.

Full-grown hornworm caterpillars devour an entire tomato plant in a day or two. You will recognize them by their giant size and the characteristic “horn” on their rear. Appearing in late spring and summer, they look first for tomato plants, but they will also attack eggplants, peppers, and potatoes.

Because they are usually not present in hordes, you can often control hornworms by simply handpicking (the horn is harmless). If you’d rather not, then dust or spray the plants with Dipel, or any caterpillar spray containing Bacillus thurengiensis. Look for this name in fine print on the label. This is an organic biopesticide that acts only on certain species of caterpillars and without harming beneficial insects. Once treated, otherwise healthy plants should recover well.

If you see a hornworm with white, oval cocoons on its body, leave it in the garden. It has been parasitized by a braconid wasp, and more wasps will emerge from the cocoons to attack other hornworms.