Tomato Hornworm

It’s amazing that such a pretty caterpillar can be so destructive. Especially when eating certain parts of your gardens and vegetables. These large & fat caterpillars feed voraciously on the leaves and fruits of your tomatoes, eggplants, potatoes, and peppers. They leave behind damaged leaves and stems with a signature dark green or black droppings. Eventually they turn into adult moths called sphinx moths or hawk moths.

Life Cycle:

The adult moths lays eggs on the underside of tomato leaves in the springtime. These eggs hatch within 6-8 days and the larva goes through 5-6 stages before reaching full growth in 3-4 weeks. At this time the full-grown larva wander from the garden area and burrow into the soil where they transform into the pupal stage. Hornworms remain in the soil and in pupal stage all winter. After winter, the moths emerge from the pupa in about 2-4 weeks where it goes to the surface of the soil and mates. Then, cycle continues with the females depositing eggs on the tomato plants for the next generation of hornworms.

Hornworms are difficult to see since they are a very camouflaged green color that matches the plants leaves. Gardeners usually spot damage to the tops of their plants before they actually see the hornworms. Hornworms do not like direct sunlight or heat so they tend to feed on the exterior of the plant at night where they can be more easily spotted. During the daytime they are more hidden on the interior parts of the plants.

There are 4 good methods to control hornworms:

1- Handpicking: This is especially good for the home gardener with smaller to medium size garden plots. They are easy to pluck off plants because of their large size.

2- Rototilling: By turning up the soil after your harvest you can destroy any pupae present.

3- Insecticides: A common spray for hornworm control is BT (Bacillus Thuringensis). There are various brands and you should always follow the instructions.

4- Biological: A natural enemy of hornworms are the parasitic wasp. These wasps seem to find the hornworms very effectively on their own so leave them alone when you see them. You’ll recognize them when you see a number of white egg-like projections protruding form the hornworms body. These are in fact the cocoons of the parasitic wasp. The parasitic wasp larvae feed inside the hornworms body during its life span and kill the host.

If you have tomatoes, peppers, potatoes, or eggplants you can expect hornworms to appear. Have no fear; they are easy to control once you identify their presence.