UMass Extension Landscape Message is Now Available

This is an excerpt on winter month. Click here to see the entire message.

Woody ornamental insect and non-insect arthropod pests to consider, a selected few:

  • Winter Moth: Operophtera brumata. The eggs of this insect, laid by the females who emerged in November of 2016 and were active through the winter months (mainly November through December when temperatures are above freezing) are currently present in the landscape and hidden in cracks and crevices of bark or beneath lichen on host plants such as oak, maple, apple, blueberry, crabapple, etc. Eggs are tiny and green when first laid, but quickly turn a red-orange color soon after. As the egg develops, it will turn a bright blue color, and then a very dark blue-black just prior to egg hatch. For more information about the life cycle and management of winter moth, please visit this newly updated (March, 2017) fact sheet: Winter Moth Identification and Management (

According to reports, winter moth eggs have begun to hatch at a single site monitored in Franklin, MA (Heather Faubert, University of Rhode Island) as of 4/6/2017. At this time, egg color change and hatch has not yet been observed at other locations in Massachusetts and Rhode Island where the emergence of winter moth caterpillars is being tracked. Reports suggest that the site in Franklin, MA typically experiences earlier egg development, hatch, and that only a very small percentage of those eggs have changed from orange to blue and even fewer have hatched as of 4/6/2017. Coastal areas also suffering from winter moth defoliation typically have later egg hatch due to cooler temperatures. We will continue to monitor winter moth egg hatch and will report any additional development reported by scouts in the next Landscape Message due April 14th. You may also visit the UMass Landscape, Nursery, and Urban Forestry Facebook page @UMassExtLandscape for announcements regarding winter moth activity.

For more information about using growing degree days to predict insect development, please visit:

Blueberry and apple growers looking to manage winter moth caterpillars early before damage to the buds can occur may consider an application of dormant oil just prior to egg hatch, when temperatures are above 40°F for at least 48 hours following application, which can help suffocate overwintering winter moth eggs if good coverage is achieved. Observe all precautions on the label regarding phytotoxicity and the environmental conditions required for increased effectiveness of the product. Once egg hatch occurs, before the tiny winter moth caterpillars wriggle their way into the expanding blueberry or apple buds (where they will be protected from insecticide applications until the buds open fully), a follow-up application of a product containing the active ingredient spinosad (which is effective by contact) can aid in protecting these crops.

For individuals managing winter moth in ornamental plants, depending on the active ingredient being used, waiting until host plant leaves open completely may be important for management, particularly if Bacillus thuringiensis Kurstaki (Btk) is the active ingredient of choice. Btk must be ingested by actively feeding, young caterpillars to be effective. Applying Btk to closed buds for winter moth management will not have the desired effect. Spinosad is also effective through contact on winter moth (including older caterpillars) once ornamental plant leaves have fully expanded, however it should not be applied to flowering plants as it is toxic to pollinators until it has dried (which can take 1-3 hours depending upon local environmental conditions). The Elkinton Lab has reported that the number of pupating winter moth in 2016 (at their study sites) was much lower than what has been observed in previous years. Reports from Hanson, MA indicate fewer winter moth eggs are present on monitored trees than in previous years. Hopefully this will translate into fewer caterpillars at least for some areas in Massachusetts this year, however one should not expect them (or the damage they cause) to completely disappear in 2017.

Winter moth is a non-native insect that was identified in Massachusetts for the first time in 2003 following persistent reports of defoliation in eastern areas of the state such as Cape Anne and on the North Shore near Cohasset, Hingham, and Rockland on the South Shore in the late 1990’s. For more detailed information about the history of this insect pest in North America and Massachusetts, please visit the newly updated (March, 2017) fact sheet: Winter Moth in Massachusetts: History and Biological Control (

This fact sheet also includes updates regarding the progress of the work of Dr. Joseph Elkinton’s laboratory group at the University of Massachusetts and their efforts towards the biological control of winter moth using Cyzenis albicans, a tachinid fly. The fly parasitizes the caterpillars of winter moth specifically. In other areas, such as Nova Scotia where winter moth was also problematic, this fly used for biological control has been successful in reducing winter moth to a non-pest. C. albicans has been released across 41 sites in Massachusetts and has been established in at least 17 of those sites as evidenced through the recovery of flies in winter moth in subsequent years. In one site in Wellesley, these flies have been observed to be spreading from the initial release location and their populations have increased alongside an observed decrease in the winter moth population there. For more information, please visit the above mentioned fact sheet.