UMass Extension Landscape Message April 15, 2011

"Winter Moth (WM) eggs began hatching in MA on April 10th as reported by Deborah Swanson in Hanson, MA (Plymouth County). Heather Faubert reported that WM egg-hatch began in RI on April 11th. New WM larvae seek and wriggle into swelling buds of the host plant and can be found there now. New larvae within buds a light in color and only about 1mm in length. Once larvae are within the buds, there are no known controls until the buds open and the caterpillars become free-feeders; Spinosad products work very well at this point. Bacillus thuringiensis (var. Kurstaki) (B.t.K.) also works well against the younger caterpillars once the foliage has emerged from the but it is important to note that if B.t. is used while the leaves are emerging, only the foliage present at the time of application will be coated with B.t., which needs to be ingested in order to be effective. As new foliage emerges over the next few days, it will not be covered with B.t. and therefore can be consumed by the caterpillars. Hopefully, foliage will emerge quickly this spring thus limiting the amount of damage that the WM caterpillars are capable of causing while in the buds. Last year 75,000 acres in eastern Massachusetts were defoliated by winter moth caterpillars. Those areas that were most affected may very well experience equal or potentially worse damage this year. Winter moth is an especially difficult insect to predict in MA and how it will behave here is still not yet fully understood given that it is a recent exotic invader to our state. Dr. Joe Elkinton at UMass Amherst continues with his studies of this pest and its population dynamics. "

Claire