The larvae pale green caterpillars or loopers, have two pairs of prolegs and a pale white stripe running the length of both sides. They are often misidentified as fall or spring cankerworms which have similar appearance and feeding pattern. Adult are the female is gray and brachypterous and therefore cannot fly.
There hosts include; Acer, Amelanchier, Betula, Calluna, Carpinus, Castanea, Corylus, Crataegus – Cydonia, Fagus, Fraxinus, Larix Malus, Myrica, Ostrya, Picea, Populus, Prunus, Pyrus, Quercus, Rhamnus, Rhododendron, Ribes, Rosa, Rubus, Salix, Sorbus, Tilia , Ulmus, Vaccinium and Viburnum.
Winter moth was introduced into North America from Europe. The first infestations were confirmed in Nova Scotia in the 1930’s. During the interceding decades winter moth has been reported in Eastern Canada on Prince Edward Island, New Brunswick in addition to Nova Scotia. Infestations in Western Canada, Vancouver and British Columbia were reported in the 1970’s. The states of Wash-ington and Oregon experienced outbreaks in commercial blueberries around this same time.
Winter moth is established in Massachusetts and Rhode Island and has been found in New Hampshire, coastal Maine, southeastern Connecticut and on Long Island, NY.
The newly hatched larvae crawl up tree trunks and disperse by ballooning on a silken strand. Larvae work themselves underneath the scales of flower and leaf buds where they begin to feed from within, completely destroying the buds. They move into new buds until the clusters start to open. During cool wet springs the damage to buds may be extensive. As the leaf buds open the small larvae cluster in the new leaves. The larvae leave the leaf clusters to feed at night. Larger larvae can defoliate host plants. Mortality is high for host plants defoliated two or more years in a row. Extensive feeding in flower buds results in greatly reduced flowering and fruit production.
Moths emerge from the soil in late fall and are active until January in temperate areas. The males are tan to light brown with fringes on all four wings. The males are strong flyers and are attracted to lights and lamps. The female is gray and brachypterous and therefore cannot fly. Adults are active from October through February. The female deposits green egg clusters in bark crevices, under bark scales and lichens and in other sheltered locations. The eggs turn orange within 3-4 weeks and become very dark just before hatch. Egg hatch is closely synchronized with bud burst, usually emerging from late March to early April in Massachusetts.