Apple Ermine Moth

Scientific name: Yponomeuta malinellus Zeller

Native range: Eurasia

At Risk

Apple ermine moth attacks apple and crab apple (Malus spp.). In the Pacific Northwest, it primarily attacks abandoned orchards and backyard trees but could also become a pest in commercial orchards by causing defoliation at the tips of branches of apple trees. Severe defoliation can cause fruit to stop growing and prematurely drop.

Distribution

Apple ermine moth has been present in the Pacific Northwest since at least the mid-1980s. It can now be found in Oregon, Washington and British Columbia. Apple ermine moth has never been detected in Minnesota. However, in May 2001, larvae were discovered in Wisconsin on nursery stock imported from Oregon. The larvae were destroyed and apple ermine moth did not become established in Wisconsin.

Biology

Apple ermine moth has only one generation per year. They overwinter as young larvae underneath old egg masses from the previous year. In early spring the larvae emerge and move to nearby developing leaves where they will mine in the leaves. Later in the spring they begin to feed in communal webs like tent caterpillars - several tents may be created in each tree. Larvae continue feeding until June, when they pupate. Pupating caterpillars line themselves up neatly in tightly packed clusters. Adult moths begin to emerge in June and lay eggs from July through September.

Identification

Adults are small - ½ inch to ¾ inch - with snowy-white forewings, grey hind wings, and long fringes on the wing margins. The upper sides of the forewing usually have 15 to 30 small, black dots arranged or distributed in three or four rows. Larvae of the apple ermine moth are varied in color and can be grey, yellowish-grey, greenish-brown, and greyish-green with a black head and two conspicuous rows of black dots running the length of the caterpillar’s back.

Regulatory Status: Potentially Regulated

If apple ermine moth were discovered in Minnesota, it is possible that actions would be taken to prevent its spread to new areas and eradicate an infestation if it was discovered prior to establishment.