Caterpillars are immature moths and butterflies. Because they feed on plants, a number of caterpillar species wreak havoc on vegetable crops and fruit trees in the home garden. Fortunately, there are many naturally occurring predators that help to keep caterpillars in check, thus reducing the need for harsh pesticides. Parasitic insects also help control caterpillar populations.
Common Garden Caterpillars
The large green caterpillars known as tomato hornworms are some of the most notorious garden pests. When present in high numbers, these caterpillars can defoliate entire plants. As their name suggests, tomato hornworms feed on the leaves of tomato plants, and they are also known to attack pepper, eggplant and potato plants. Meanwhile, vegetables in the Brassica family, such as cabbage, broccoli, Brussels sprouts and cauliflower among others, are often attacked by caterpillars that are known as cabbageworms.
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Other types of caterpillars attack trees. The eastern tent caterpillar, for example, often infests stone fruit trees, like peach trees, cherry trees and plum trees as well as apple and crabapple trees. Eastern tent caterpillars build nests beneath the point where limbs connect. The nests may be large and may become an eyesore. The nests of eastern tent caterpillars may be confused with those of another species: the fall webworm. You can differentiate between the two, however, because fall webworms build their nests at the end of branches.
Bugs That Eat Caterpillars
A number of bugs are considered beneficial because they prey on caterpillars and other garden pests. Insects known as lacewings are among the top predators of caterpillars. Depending on the lacewing species, larvae or adults or both may feed on caterpillars when they are small, including the tomato hornworm. While you may not think of wasps as beneficial, paper wasps also eat caterpillars, helping to keep several pests under control, including the tomato hornworm and cabbageworms. Ladybugs are also important predators of tomato hornworms.
Insects known as yellow jackets, which are related to paper wasps, also consume caterpillars. However, they can quickly become a nuisance to humans because of their tendency to sting. Like bee stings, yellow jacket stings can be fatal for people who are allergic to them. Yellow jackets are not picky eaters and will eat fruits, vegetables, baked goods, candy and many other foods, making them unwanted picnic guests.
Other caterpillar-eating insects include generalists like ambush and assassin bugs, which feed on a number of pests, including the fall webworm. Ground beetles, tiger beetles and the larvae of syrphid flies also prey on caterpillars.
Other Biological Caterpillar Controls
Some insects, mostly wasps, have a parasitic relationship with caterpillars. For example, female ichneumonid and braconid wasps use their stingers to lay eggs inside caterpillars, such as tomato hornworms. When the eggs hatch, the wasp larvae destroy the caterpillar from the inside. Some species of wasps lay their eggs inside moth and butterfly eggs, preventing the larvae that eventually become caterpillars from hatching.
Birds and some species of spiders also eat caterpillars. Birds most commonly exhibit this behavior when they are feeding their young.
- University of Minnesota Extension: Tomato Hornworms in the Home Garden
- NC State Extension: Paper Wasps for Caterpillar Management in the Landscape
- Utah State University Extension: Caterpillar Pests of Brassica Vegetables
- University of Wisconsin Extension: Assassin Bugs and Ambush Bugs (Reduviidae)
- University of Kentucky College of Agriculture, Food and Environment: Eastern Tent Caterpillar
- PennState Extension: Fall Webworm
- Michigan State University Extension: The Rise and Fall of the Fall Webworm
- University of California Statewide Integrated Pest Management Program: Natural Enemies of Caterpillars
- Clemson University Extension: Yellow Jackets
- Clemson University Extension: Natural Enemies - Predators and Parasitoids