New Invasive Pest Arrives In MA: Elm Zigzag Sawfly Threatens Elm Trees

MASSACHUSETTS — The list of invasive pests threatening native trees in Massachusetts just got longer.

A state Department of Conservation and Recreation investigation recently confirmed that elm zigzag sawflies are active in the state. DCR determined that the invasive pest defoliated elm trees located near Becket in the Berkshires, and is now spreading east.

"Since the original detection of the invasive species, populations have been found in Berkshire and Hampden Counties. At this time, staff have not yet determined how the species was introduced to Massachusetts. DCR foresters are working to identify the extent of infestation in the state," the DCR said in a recent news release.

Zigzag sawflies are native to China, and were seen for the first in North America in 2020 in Quebec. It's unclear how the pest made its way across the world to the Northeast. The sawfly larva live on elm trees and feed on leaves when they emerge from cocoons.

The discovery of the species comes on the heels of the recent confirmation of box tree moth activity on Cape Cod, another invasive first. Box tree moths can cause complete defoliation and death of boxwood shrubs.

State conservation officials have mainly been concerned about the recent spread of the spotted lanternfly in Massachusetts in recently years. Lanternflies, also native to China, were first confirmed in the state in 2020 in Milford and Norwood, but have been confirmed in many East Coast and Midwest states.

Several Central Massachusetts communities, including Worcester, Shrewsbury, Boylston, West Boylston and a portion of Auburn, are still under a federally-mandated quarantine due to the discovery of Asian longhorned beetles. The beetles are a major threat to hardwood trees.

Zigzag sawflies have also been confirmed in Virginia, Pennsylvania, New York, North Carolina, Maryland and Vermont. DCR is asking any homeowner who sees an elm zigzag sawfly to report the sighting to the Forest Health Program.