It’s a bit early to bring it up this year, but those small green worms always prompt questions as they begin dangling from trees during the march toward spring.
They’re called canker worms, and they can wreak havoc on the foliage. Many of our neighbors prepared this year by banding their trees. Did you?
These fall canker worms, sometimes known as inch worms or loopers, have spent the winter climbing to the tops of trees and laying their eggs. Bands on some trees have helped reduce the numbers.
Meanwhile, there’s another variety in our area called – not surprisingly – spring canker worms. It’s a different species and according to biologists at N.C. State University, both types feed on our leaves.
In spring 2012, willow oak trees were most heavily damaged in North Carolina, including the Charlotte area, according to NC State experts. They say the worms can completely defoliate trees, though that’s not always guaranteed. Says Steve Frank, an N.C. State assistant professor of entomology:
“Last year it was most common for affected trees to lose 10-50 percent of their leaves. A year or two of defoliation will not affect the long-term health of large trees. However, they will be ugly the year they are defoliated and it causes extraordinary concern among the public.”
It appears that one of the reasons for infestations here in recent years has been the disappearance of a parasitic wasp that usually controls the canker worm population. These wasps lay their eggs inside canker worm eggs, killing them. Tasnim Shamma of our news partner WFAE-FM reports that entomologists aren’t sure why the wasp has not been reproducing well in Charlotte for the past 25 years.
“The population (of canker worms) went up and it never would go down,” Charlotte city arborist Donald McSween told WFAE. “So the population was very high every spring. We had thousands, millions of caterpillars eating all the foliage of our trees. That can be a nuisance but the major thing was repeated defoliation of these large old trees, threatens their health.”
Experts say banding and insecticide are the best defenses. Find more information on WFAE and the other sources below.
Feb. 18, 2013, WFAE.org, “A Trifling Place” podcast, “A Trifling Place, Episode 6: When Cankerworms Attack”
Nov. 8, 2012, North Carolina State University’s The Abstract, NCSU.org, “Stick it to canker worms.”
March 27, 2012, DavidsonNews.net, “Pets or pests? What are those little green worms?”