NC State: Lack Of Plant Diversity Fuels Cankerworm Damage

May 27, 2014

North Carolina State University researchers are looking into stopping an invasive species of caterpillar that can damage and kill urban trees and shrubs.   

Cankerworms like this one can chew through shrubs and leaves on trees that beautify urbam landscapes.
Credit Steve Frank

Cankerworms are born from the eggs of wingless moths.  The moths climb the trunks of trees to nest in the winter.

N.C. State professor and entomologist Steve Frank says these young larvae do most of the damage to trees and bushes that dot the city landscape.

"And then in early Spring just as the leaves are opening on the trees, the cankerworm eggs hatch and the caterpillars start eating the leaves," says Frank. 

"They feed for 4-6 weeks, and then they form a cocoon in the soil and they stay there until the next winter."

Frank says several North Carolina cities have turned to sticky bands around trees  to keep the moths from scaling them to lay their eggs.

"It's a technique that a lot of municipalities use," he says.  "Charlotte uses it in some of its neighborhoods and Durham uses it in some of their neighborhoods.  And it seems like on a large scale, it can work reasonably well to reduce damage.  But the caterpillars can move around a lot from tree to tree."

Frank says that's because the silks that the worms produce and swing on are blown between plants by the wind

He says a lack of diversity in plant life within city limits are another reason for the cankerworm damage.   Frank's research finds that cankerworm is much less apparent in naturally-growing areas like state parks.  His work is published in the journal Urban Ecosystems.