Pest Identification: Inchworm
Most Common Types
Inchworms are the larvae of moths from the family Geometridae. They are also known as cankerworms, measuringworms, and loopers.
What They Look Like
Inchworms are green, brown, or black with smooth, hairless bodies around 1-inch long. They often resemble the twigs of trees and shrubs they feed on. The inchworm resembles a caterpillar that lacks appendages in the middle portion of the body. An inchworm has three pairs of true legs at the front and two or three pairs of larval appendages called prolegs at the rear.
Where They Live
The family Geometridae is the second largest of all the butterflies and moths with about 35,000 species worldwide. Around 1,400 species occur in North America. Inchworms live in areas where woody trees and shrubs are found.
Where They Nest
Inchworms begin life as eggs that are attached to the underside of leaves. The eggs hatch in spring and the inchworms molt as they grow.
Steps to Prevent
The best way to prevent infestations is to create a hospitable environment for natural predators of the inchworm, like ground beetles, birds, yellow jackets, and Trichogramma wasps. The use of chemical pesticides is not recommended to control inchworms. A large infestation with significant damage may warrant the use of horticultural oils which can be applied to trees. Inchworms in vegetable gardens may be controlled by using the biological pesticide Bacillus thuringiensis.
Are They Harmful?
Inchworms are not harmful in small numbers in their natural habitat, but can be destructive to pines, fruit trees, garden plants, and vegetable crops when infesting in them.