New York’s Elm trees are facing a new threat from an exotic pest. The state DEC says the elm zigzag sawfly was detected for the first time at three locations in St. Lawrence county.
The pest feeds exclusively on Elm trees and can cause severe defoliation, branch dieback, and crown thinning. DEC officials said in a release the pest has not been shown to cause tree mortality, but repeated defoliation by established sawfly populations would put added stress on native elm trees already heavily impacted by Dutch Elm disease.
One concern is how quickly the pest can spread. The sawfly is capable of flying up to 56 miles in a year, perhaps further when assisted by the wind. That means Elm trees almost anywhere in the state could eventually be impacted, though DEC officials said the populations appear to be low and causing minor damage for now.
The insect can also reproduce quickly, laying up to 60 eggs at a time four to six times a year. DEC officials say the sawfly was discovered in southern Quebec in 2020, and the DEC began surveying for the pest along the US-Canadian border the following year.
Additional surveys will be performed throughout the fall to determine the extent of the sawfly's presence and impact in the region.
