Spring defoliator damage to shade trees
Editor’s note: This article is from the archives of the MSU Crop Advisory Team
Alerts. Check the label of any pesticide referenced to ensure your use is
included
Don’t get too excited by all the holes in your tree leaves, because
caterpillar feeding damage does not affect tree health until more than
30 percent of the tree canopy is removed, and 30 percent canopy loss
means that 1/3 of every leaf has been eaten, or 1/3 of all the leaves
are gone. That level of feeding injury is rare and usually only happens
with occasional outbreaks of gypsy moth, eastern tent caterpillar,
forest tent caterpillar, fall webworms, orange-striped oakworm, mimosa
webworm and a few others. Most of the feeding damage that I have seen on
shade trees this week has been caused by spring and fall cankerworms.
Cankerworms are caterpillars with only two or three pairs of fleshy
prolegs instead of the standard five pairs of prolegs that most
caterpillars have. This causes them to “inch” or “loop” when the walk,
and is why many people call them inchworms or loopers. Cankerworms
rarely cause enough feeding damage to hurt shade trees, and the same is
true for a large group of caterpillar species that are often referred to
as “spring defoliators.” Enjoy the inchworms and don’t worry about your
tree.