Tomato hornworms are ghastly looking creatures with a sharp horn on the tail end and creepy eyes along both sides. The worm is actually a caterpillar that will emerge as a moth in June and July. Tomato hornworms feed on leaves, stems and fruit of all the nightshade family of plants, including the tomato and eggplant. Here's what to do if you have this uninvited guest.
Things You'll Need
- Parasitic Wasps
Look for tomato hornworms on the foliage of tomato plants. They are very difficult to spot. One way to find them is to look for the black excrement on the tops of the leaves, then look at the set of leaves above. Usually the caterpillars are right in view, but their effective camouflage makes them very hard to see.
Pick the caterpillars by hand and squash underfoot if you have the stomach for this kind of grisly work.
Spray Bacillus thuringiensis (or Bt) while the problem is still in the caterpillar state. Bt is a bacteria that is safe to use on food crops and very effective in the control of caterpillars.
Purchase parasitic wasps, which will lay eggs on the tomato hornworm caterpillar. The wasp eggs hatch and the young feed on the caterpillar. (Parasitic wasps are not harmful to humans.)
Tips & Warnings
- The moths lay eggs that hatch in only one week, turning into the large 4 1/2- to 5-inch green caterpillar, then pupate in the soil to hatch again next year.
- Allow young children to view and observe this insect. It is fascinating not only for its size, but also for its colorful markings. Tomato hornworms are not harmful to humans - they only look that way.
- Always use the least toxic method of pest control as your first step.
- It is not recommended that you use chemical pesticides on food crops.
- Only mix the amount of Bt that you will use at one time.
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