Winter Moth, Spring Management

Over the past few years defoliating insects called winter moth have infested over a million and a half acres of trees in New England with areas of greater Boston experiencing extensive damage. Increasing winter moth populations in Eastern Massachusetts continue to threaten already weakened trees and spread to previously unaffected areas. Winter moth adults emerge to mate in late fall through early winter.

Preventative treatments are effective but require precise timing when the insects are most vulnerable.  Barrett Tree Service East utilizes a new class biorational pesticides which offer the efficacy of synthetic materials with the benefits of biological controls. We have found these insect control products provide effective pest control with minimum impact to beneficial insects and other organisms.

Winter moth (Operophtera brumata) is an invasive pest in Massachusetts that feed on a wide variety of deciduous hosts including oak, maple, cherry, crabapple, blueberry and azalea. Once winter moth hatch in early spring, the larvae (resembling green inchworms) burrow inside buds and feed on juvenile leaf and flower tissue until mid-June.  Partial defoliation leads to branch mortality and complete defoliation can result in total tree mortality.

Dr. Joseph Elkinton, a forest entomologist at the University of Massachusetts estimates that heavily infested areas average 2000-3000 females per tree, each producing up to 150 eggs. On average, that’s about 250,000 caterpillars, per tree! “It’s going to look like a lot of shotgun blasts went through the leaves in these neighborhoods, if the trees aren’t completely defoliated,’’ according to Dr. Elkinton.

Winter moth is an invasive pest that feed on a wide variety of deciduous hosts. Image:

Because it is not native to this area, the winter moth has no natural predators. Since 2005, researchers at Elkinton’s lab have been trying out a solution that has proved successful in Europe, Nova Scotia, and British Columbia. Parasitic flies (Cyzenis albicans) have been strategically introduced in selected areas in the eastern part of the state. The flies lay eggs which are ingested during caterpillar feeding. The fly begins to devour the caterpillar from the inside which eventually kills it.

Winter moth larvae resemble inchworms. Image:

While the potential for damage to deciduous foliage is high, winter moth can be effectively controlled. Preventative treatments require precise timing, beginning in early spring before leaf and flower buds open.  Barrett Tree Service East chooses to use bio-rational control materials. These innovative products, often derived from naturally occurring organisms, provide effective insect control while minimizing impact to the environment and other non-target organisms.

If you have seen evidence of this insect (previous defoliation, green inchworms, or moth flight in December), contact a Certified Arborist at BTSE to discuss strategies for protecting your important trees.

For additional information on winter moth visit UMass Extension (