Scientific name: Operophtera brumata, L.
Native range: Europe
There are no federal, state or local regulations in place regarding winter moth. If winter moth were found in Minnesota, actions may be taken to restrict the movement of materials that could spread winter moth as well as measures to suppress or eradicate any infestations.
Winter moth was originally introduced to Nova Scotia from Europe in in the 1950s. It spread throughout eastern Canada and was detected in western Canada in 1970. In the United States, winter moth was discovered in Massachusetts in the late 1990s and has since spread to the eastern half of Massachusetts (where is has become a dominant spring defoliator), Rhode Island, Connecticut, Long Island, southeastern New Hampshire, and southeastern Maine. It is also present in Oregon and Washington.
It is likely spread to new areas through movement in plant material such as firewood, ornamental plants, and nursery stock containing soil.
Winter moth completes one generation per year. Eggs hatch in April, and larvae feed on expanding buds and newly formed leaves. Larvae are done feeding in late spring to early summer and drop into the soil to pupate. The entire summer is spent as a pupa within the soil until late fall to early winter when adult moths emerge to mate. Eggs are laid individually or in groups in bark crevices or other protected places. Winter moth is a cyclical pest in its native range, but numbers have remained consistently high for a number of years in Massachusetts. Similar to European gypsy moth, female winter moths are not capable of flight, but larvae can spread on silken threads (called ballooning). Another similarity to gypsy moth is the ability of winter moth egg masses to be spread on firewood or other outdoor materials. In addition, winter moth could be spread in potted nursery stock or other plants due to their habit of spending the summer as a pupa in soil.
The adult male winter moth is tan to brown with a wingspan up to 1¼ inches with fringed forewings that have bands of black hatch marks. The female moth is gray to black and flightless. Winter moth larvae are lime green and often referred to as inchworms or looper caterpillars with faint white to creamy-yellow stripes running lengthwise along each side of the body. The pupa is brown with two short spines at the end.
Winter moth is similar in appearance and life history to fall cankerworm which is common in Minnesota and also Bruce spanworm which is not commonly seen in Minnesota.
Host Plants and Impact - Winter moth primarily feeds on deciduous plants. Common hosts include, but are not limited to, oak, maple, birch , basswood, ash, elm, apple, and crabapple and blueberry. Feeding can completely defoliate trees, leaving only the veins. Most damage occurs inside the bud before the leaves expand. In Minnesota, the orchard, forestry, and berry-growing industries may be most impacted if winter moth were to become established. It could also become a shade tree pest.
Contact the Minnesota Department of Agriculture via Arrest the Pest if you suspect you have found an infestation of winter moth.