Winter Moth

Operophtera brumata

Invader Images

    • Winter moth larva
    • Winter moth larva
    • Winter moth eggs
    • Winter moth adult
    • Damage by winter moth
    • Winter moth damage
    • Winter moth damage
    • Winter moth larvae

Identification

The winter moth (Operophtera brumata) feeds on deciduous plants including Maple, Oak, Cherry, Basswood, Ash, White Elm, Apple, Blueberry, and other perennials. It is commonly observed in late fall/early winter as a white-ish adult moth and, in spring, as a tiny green caterpillar. 

Winter moth caterpillars feed on the leaves of their host species. High populations of the pest can completely defoliate the host plant, inhibiting its ability to grow and leaving it vulnerable to other insects, diseases, and eventual mortality. 

See image gallery above for signs and symptoms.

Biology

Origin

The winter moth is native to Europe. It was transported to the United States via Nova Scotia in the 1950s, most likely within the soil of ornamental landscape trees.The invasive insect has since spread into Eastern and Western Canada and the United States.

Life Cycle

Adult winter moths emerge from the ground in November and December. The fully developed adult moths immediately begin the reproductive process. The female winter moth, unable to fly, climbs up trees or buildings and attracts males to her with pheromones. After mating females lay a cluster of approximately 150 bright orange eggs under tree bark and in crevices; immediately dying following the dispersal of the eggs. 

In March and April, when temperatures reach approximately 55°F, the eggs hatch into smooth green inchworms. The newly hatched caterpillars are approximately a half inch to an inch in length and have a white stripe lengthwise on each side of their bodies. The young caterpillars disperse up into the plant's canopy by spinning a strand of silk and riding wind currents up, a method known as “ballooning”. Once in the canopy the caterpillars feed on the foliage, both open leaves and within tree buds. In mid-June, the caterpillars migrate into the soil to pupate. Fully grown winter moths will emerge from these pupae in November and December.  

threat

The winter moth is a species of particular concern because it damages a wide variety of tree and agricultural crop species. High populations of the pest can cause complete defoliation. Repeated years of defoliation may contribute to tree decline.

Management Options

  • Do not import plants or soil from infested areas. New infestations have been traced to moving winter moth along with landscape plants since its cocoons are in the soil from June through November.
  • Winter moth can be indistinguishable from its native relative, the Bruce spanworm, and they can hybridize. Researchers are looking for populations of either species to better understand their range and potential impact. Look out for lacy foliage and feeding inchworms early in the spring.

Vermont Distribution

Winter moth has never been detected in Vermont.

Citations

Photo Credit

Dimitrios Avtzis, NAGREF-Forest Research Institute, Bugwood.org

Fabio Sterguic, Universita di Udine, Bugwood.org

Gyorgy Csoka, Hungary Forest Research Institute, Bugwood.org

Hannes Lemme, Bavarian State Research Center for Agriculture, Bugwood.org

Milan Zubrik, Forest Research Institute - Slovakia, Bugwood.org

information credit

Mass Audubon

Massachusetts Introduced Pests Outreach Project

US Forest Service Pest Alert