Where Are the Cankerworms This Year? We Asked an Expert.

For the past three decades, the emergence of cankerworms has accompanied the blossoming flowers and running weather during spring. This season, the little green caterpillars that always seem to find a home on cars or people’s heads were nearly absent throughout the city—and people noticed. Where were they this year?

“There is not a definitive answer but we have some ideas,” Bill Hilton Jr., executive director of Hilton Pond Center for Piedmont Natural History explains. “The weather has been a factor, so whenever you have a cold winter you’re going to lose the adult females and they won’t be able to lay eggs.”

By mid-April, cankerworms typically hatch by the hundreds from female wingless moths that laid eggs on tree branches in the winter. In years past, adhesive bands around the tree trunks and chemical treatments on leaves helped keep the cankerworm population under control.

Since the cold air crept into spring, cankerworms that did hatch were unable to thrive in such harsh temperatures and with limited vegetation. Newly hatched cankerworms feed on the soft tissue of fresher leaves and with greater lengths of cold temperatures, fewer leaves bloomed in time for cankerworms’ nourishment.  

But although these inchworms can be troubling for citizens, their ability to defoliate trees is rare, and minor compared to the role they play in the ecosystem.  “They serve as an important food source for the spring migratory birds,” Hilton says. “Their migration timing has historically coincided with the ‘bug burst,’ so that could be another reason we’re not seeing as many cankerworms.”

Hilton points more towards the possibility that the spring migratory birds arrived from the tropics just in time to dine on the newly hatched worms. Although the city dodged cankerworms this season, come next year, they may be back.

The cankerworm issue was part of our list of 24 Solutions for Charlotte in September.