Canker WormsSpring and Fall Cankerworms
Cankerworm is an older name for what are now commonly called inchworms, loopers, measuring worms or spanworms.
The male moth has a wing expanse of 7/8 to 1¼ inches. The forewings are thin and silky with an ash gray color. The hind wings are similar but paler. The wingless female is nearly ½ inch long and generally a dark ash gray with a black dorsal line. Each sex has minute reddish spines in dorsal rows on the abdomen, which gives the dorsum a reddish aspect.
The caterpillar has a sooty (grayish-white) head, mottled with brown, and five pairs of legs. When full grown, the caterpillars are 3/4 to 1 inch in length, and vary in color from reddish to yellow-brown, green, blue-black or an intermediate color. The broadly oval eggs are a shiny white when first laid, but change to yellow-brown with age.
The moths appear in April and May and lay small irregular clusters of 50 or more eggs in bark crevices on the host tree. Hatching and larval feeding occur in early May, about the same time as with the fall cankerworm. When full grown, the larvae enter the soil and pupate. The larvae overwinter in a bare earthen cell and pupation occurs in late winter.
Both fall and spring cankerworms feed on a wide variety of trees including apple, ash, beech, elm, hickory, linden, maples and oaks.
Control by trapping the wingless females or spraying the active larvae after they start feeding on tree leaves.
Photo courtesy of USDA Forest Service - Northeastern Area Archives, USDA Forest Service, www.forestryimages.org
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