Hornworms

Hornworms are very large caterpillars (up to 5" long) that are the larvae of the sphinx (or hawk) moth, a large moth that is sometimes referred to as a Hummingbird moth because of their size and the way they fly. They are bright green with diagonal white stripes on their sides and a characteristic red or black horn at their back end. Tomato hornworms have a rather straight black horn and tobacco hornworms have a slightly curved reddish horn. Both are common pests in the vegetable garden.

Damage to plants

Hornworms can be serious pests of tomatoes, peppers, potatoes, and even eggplants. They devour the leaves of these plants and because of their large size, they can defoliate a plant very quickly. Their camouflage coloring combined with the fact that they feed from the undersides of the leaves makes them very difficult to spot in the garden. Fortunately the large fecal pellets (frass) is quite easy to spot and this can help reveal their location.

Control Measures

• The easiest way to get rid of hornworms is to find them on your plants and pick them off - no sprays involved!
• A small parasitic braconid wasp (Cotesia congregatus) lays its eggs on the back of these caterpillars. The larvae that hatch from the eggs feed on the insides of the hornworm and then pupate (form little cocoons) on the back of the hornworm. If you find these parasitized hornworms in the garden, be sure to leave them there because the hornworms will soon die and the little wasps will hatch out and stick around to parasitize other hornworms!
• Bonide Thuricide (Bacillus thuringiensis) is a bacteria that selectively infects and kills caterpillars, especially when they are young and small. It is less effective on the large, mature hornworms. Always follow label directions.   

• ALWAYS READ and FOLLOW the LABEL directions when using any pesticides.