Cankerworm Prevention

The fall cankerworm is a moth native to North America.  This insect gets its name because the adults emerge from pupae in the fall, mate, and lay eggs – the eggs are the overwintering stage.  Females are wingless, and males are generally a gray color.  Caterpillars are also called “inchworms” because they bring their back legs to the front legs and “inch” along as they move.  Young caterpillars “skeletonize” the leaf, but older larvae (which grow to about an inch long) will consume the entire leaf.  Oaks seem to be the preferred host plant, but this insect has a wide host range, and feeds on many hardwood species throughout the eastern U.S.  The fall cankerworm has one generation per year, and populations can occasionally reach outbreak levels.  During outbreaks, entire trees may be stripped of foliage; successive defoliations can weaken trees.  Natural enemies (including parasitic wasps and predatory beetles) help keep populations under control.  Insecticides are effective control methods, and some physical barriers (e.g. tree banding) are effective on single or high-value trees.