Tomato Hornworm Caterpillar - How to Control This Garden Pest?

picture of tomato horworm
Photo by Khanm83

Any veggie gardener would like to grow perfect tomatoes in his vegetable garden. However, there are large pests, attempting to devour your plants, and spoil the crops. Could it be the tomato hornworm (Manduca quinquemaculata)? Discover, how to find and control this pest.

What is tomato hornworm life cycle?

Hornworms feed on host plants from the Nightshade (Solanaceae) family, such as tomatoes, tobacco, eggplants, peppers and potatoes. You can find the pests on leaves, stems and fruits. Just a few of them can destroy the plant.

A hornworm life cycle starts, when adult moths mate and lay their eggs on leaves of a host plant. After a few days, the larvae, in the form of a caterpillar, hatch. These catterpillars feed on your veggies and enlarge quickly. When fully grown, they pupate and overwinter in the soil. In warmer climates, 2-4 generations of the horned worms can mature during one season.

How to recognize tomato hornworms?

How to find out, whether your tomatoes are attacked by hornworms, or another type of a pest? First, you will see, that plants have areas, which had been chewed on. Huge piles of black droppings, attached to the leaves of a host plant, are the telltale sign of a hornworm presence.

Manduca bugs are difficult to spot, since their colors tend to blend very well with green shades of tomato leaves. How do these pests look like? Large (4-5 inches), green catterpillars sport black horns on their rear ends, true to their name - hornworms. Eight V-shaped lateral white or grayish markings characterize this pest (see the picture above).

You can usually find those insects on the downside of the stems or leaves of the host plant. They look scary, but are completely harmless to the humans. Your kids may even enjoy seeing this interesting pest.

Gardeners often confuse tomato hornworm with tobacco hornworm (Manduca sexta), since both species can feed on the same plants. Mistaking tomato and tobacco hornworms doesn't matter, as the control techniques are identical in both cases.

How to control tomato hornworms?

picture of tomato horworm wasp parasite
Photo by By Stsmith, CC-BY-SA-3.0

There are a few ways to get rid of tomato hornworms:

  • Collect the catterpillars by hand and drown them in the bucket.
  • Use organic bacterial insecticide containing Bacillus thuringiensis var. Kurstaki. It's completely safe for your vegetable plants, people and any other insects. Make sure to prepare the required dose of BT just before you apply it, as storage diminishes an effectivness of the substance.
  • Use a strong chemical insecticide. This is rarely necessary, but can help, if caterpillars attack in large groups.
  • Rototill the soil in the fall or early spring to destroy the burrowing pupae.
  • Hornworms have a natural enemy - parasitic wasps, whose larvae feed on the catterpillars. When you notice the white cocoons attached to the bug (see the picture above), let them be. Next generation of wasps protecting your garden will pupate soon. Insects, such as ladybugs, eat hornoworm eggs as well.

While hornworm caterpillars seem dangerous, they are easy to fight. Apply these pest control tips and enjoy healthy tomato plants again.