UMass Extension Landscape Message May 25, 2012
"Winter Moth caterpillars are quickly approaching pupation in the warmer regions and feeding damage for the year will cease. This year has been very challenging for researchers given the warm winter, very warm late winter and early spring, and at least one freeze event after egg-hatch. In the greater Boston area and inland, winter moth damage is spotty but in Southeastern MA and westward to Providence, Rhode Island defoliation of host trees is severe. Sections of Cape Cod have also experienced near-complete defoliation from this insect this spring. An application of a product that contains Spinosad as the active ingredient should provide excellent results at this time but in some cases it is too late given the level of defoliation already inflicted on the trees. Many pyrethroid insecticides are labeled for caterpillars as well. Pyrethroids can be very harsh on pollinators, such as bees. Spinosad products are toxic to bees at the time of application but this threat diminishes significantly 24 hours after application."