UMass Extension Landscape Message May 11, 2012

Soil temperatures are averaging 56 degrees in MA, ranging from a low of 52 degrees to a high of 60 degrees in the different regions. (see table of 2012 Growing Degree Days).

"Winter Moth remain actively feeding but areas of high infestation appear to be randomly dispersed. Also, stages of the caterpillar seem to vary widely from the greater Boston area through southeastern MA and out to Cape Cod. In the greater Boston area, the caterpillars appear to be nearing pupation, in some cases, but farther south towards the Cape, they are 1-3 instar stages behind. In all areas, it is now too late for a spray of Bacillus thuringiensis Kurstaki (B.t.K). An application of a product that contains Spinosad as the active ingredient should provide excellent results at this time and throughout the caterpillar feeding stage. Many pyrethroid insecticides are labeled for caterpillars as well. Avoid spraying apples and crabapples with Spinosad or pyrethroid products if they are in bloom. 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."

Claire