Tomato: Tomato hornworm

• Categories: Tomato Tomato Insects Vegetables
• Last review date: 2024-06-05 02:10

Biology

The tomato hornworm is the larva of a sphinx moth. The adult moth has a wingspan of up to 4″-5″. Wing color is generally mottled gray. Mature caterpillars may reach up to 5″ in length but are typically around 2″ long. They are generally pale green with some white markings, although dark purple hornworms are sometimes seen. The mature hornworms are characterized by a short, curved, green to reddish horn on the back end. The larvae feed on the leaves of tomato, potato, and related plants and may cause serious defoliation. Symptoms of feeding include leaves chewed down to the midrib and dark pellets of frass (excrement) on or under plants.

Management Options

See "Using Integrated Pest Management (IPM) in the Landscape" for successful problem management techniques.

Non-chemical Management

Select non-chemical management options as your first choice!

• Hand-pick and kill hornworms. This is usually sufficient control for the home garden.
• Natural enemies including birds, spiders, and parasitic wasps help control caterpillar populations. Avoid use of broad-spectrum insecticides which can kill beneficial insects.

Chemical Management

• Apply Bt when first noticed. Hornworms will soon quit feeding but may remain on plant a few days.
• If Bt is chosen, be sure to apply when insect is feeding.
• The best time to apply is when caterpillars are young.
• Use a spreader-sticker with liquid Bt formulations.

Approved Pesticides

If you choose to use a pesticide, some examples of products that are legal in Washington are listed below. Some products are labeled for just INDOOR or just OUTDOOR use, or may allow both uses. Be sure to choose a product appropriate for your situation. Always read and follow all label directions.

• Bonide Thuricide BT Concentrate
  Active ingredient: Bacillus thuringiensis subsp. kurstaki
  EPA registration number: 4-226
• Bug Buster-O [Organic]
  Active ingredient: pyrethrins
  EPA registration number: 1021-1771-54705
• ferti-lome Dipel Dust
  Active ingredient: Bacillus thuringiensis subsp. kurstaki
  EPA registration number: 7401-290
• Safer Brand Caterpillar Killer for Trees, Shrubs and Vegetables Concentrate II [Organic]
  Active ingredient: Bacillus thuringiensis subsp. kurstaki
  EPA registration number: 70051-106-42697
• This list may not include all products registered for this use.