UMass Extension Landscape Message May 10, 2013

"Winter Moth - Population numbers appear to be on the low side for much of the coastal areas in MA. Damage thus far is minimal. Larger population numbers are higher in the Harpswell, ME population. Early scouting there suggests an average number of 8 caterpillars per bud as reported by the Elkinton lab here at UMass. Numbers may be higher on Cape Cod than they are in Southeastern MA this year. Fine silken webbing can be now found on many maple species, which is typical for winter moth once the caterpillars have become settled on a host plant. Oaks, birch, crabapple, apple, blueberry and roses are also among the common host plants for this insect here in MA. The caterpillars are still rather small in physical size and close inspection is required when monitoring. Any insecticide that contains Spinosad works well. Bacillus thuringiensis Kurstaki (B.t.K.) also works well but must be ingested by the young caterpillar in order to be effective. Leaves that are not yet fully expanded but treated with a spray of B.t.K. will quickly continue to produce more leaf tissue daily that is not covered by the spray and therefore allowing caterpillars to potentially consume more foliage before ingesting the bacterium. Many pyrethroid insecticides are also labeled for this pest but tend to be harsher on foraging pollinators, such as bees, and other beneficial insects and predatory mites. Monitor host plants now and treat where necessary. The Elkinton lab has begun their annual releases of the parasitic fly Cyzenis albicans in MA, Maine, and Rhode Island already for this year."

Note: "The Elkinton lab has begun their annual releases of the parasitic fly Cyzenis albicans in MA, Maine, and Rhode Island already for this year."

Claire