Last November the season's first hatch of winter moth fluttered into the chilly air. You likely saw the small beige moths; flying mostly at dusk and at night, they are attracted to lights—streetlights, your car headlights, even the glow from your house windows.
Come spring (usually mid-April, though the time varies with weather conditions), larvae of those moths emerge from tiny eggs, climb to the nearest bud, and feed on the tenderest foliar tissues as the bud opens. The result: leaves with large holes, chunks taken out of the edge, or entirely skeletonized. Susceptible trees include oaks, maples, linden, elm, crabapples, apple, and cherry. Repeated years of this stress can weaken a tree and lead to its untimely death.
Winter moth has been in this area only for the last ten or fifteen years. While UMass entomologists have been researching insects that might be natural predators for winter moth, they have not yet found predation remedies effective enough to prevent defoliation once an area is infested. Winter moth pesticide treatments are generally safe for vertebrates—that’s humans, dogs, cats, birds, chipmunks, etc.—though they may affect other invertebrates and insects beside winter moth. There is a great explanation of the winter moth life cycle and treatments here.
If you have noticed extensive leaf damage in the last couple of years but have never had your trees sprayed for winter moth, you may want to spray this year and limit the stress your trees are experiencing. If you have been spraying for this pest over the last several years, you may consider taking a year off, to allow other invertebrates a chance to repopulate the area.
Arborists often offer incentive discounts to customers who sign spring spray contracts in January-February. Now is the time to make arrangements with your arborist to protect your trees from winter moth in Spring 2014.