Species

Apple Ermine Moth- Yponomeuta malinellus.
Phylum: Arthropoda
Subphylum: Uniramia
Class: Insecta
Order: Lepidoptera
Family: Yponomeutidae
Subfamily: Yponomeutinae
Genus: Yponomeuta

Originated in Europe and Asia. The Apple Emine Moth was first seen in the United States in New York in 1909. It quickly moved into Canada with populations being seen in New Brunswick in 1917 and in Ontario in 1957.

It was first discovered in the Pacific Northwest in 1985.

Globally it is found in British Isles, North Korea, South Korea, Japan, Sweden, Finland, Russia (Siberia), China (Manchuria), Iran, and Pakistan.

Related Species
Western Tent Caterpillar (Malacosoma californicum) - Puget Sound Area
Forest Tent Caterpillar (Malacosoma disstria) - A rare species

Host/Site

The Apple Emine Moth feeds exclusively on Apple and Crabapple Trees (Malus spp.).

Identification

Appearance
The moth is a snowy white color with many dark spots located on its wing. Its hind wings are a grey or leaden color. Eggs are yellow, ovular shaped and around 1/8 in. in diameter. After a period of about two weeks they change to a bright reddish color. The eggs are soft and have a center area that is slightly raised. Larvae are anywhere from grey, green, brown, to yellow, and can be anywhere from 15-20mm in length. The moth's pupae are found enclosed in a grayish white cocoon, suspended in clusters. They can be up 10-12 mm long and 3 mm wide.

Indicators
The moth cocoon can be found on the leaves of an apple tree. You can usually find moth larvae feeding on tree bark. Defoliation can be seen around May or June. Caterpillars can be found eating the fruit.

Life Cycle

There is 1 generation per year. The female lays eggs 10-80 eggs in overlapping rows from June to August. During the winter, young larvae feed on the bark of trees. After the winter, larvae move to unfolding leaves of buds that are adjacent to their egg. This is where they mine leaves and later feed in a communal web toward the end of blossoming. Some of the larvae move on to the feed on apple leaves, the upper epidermis and parenchyma. Communal webs are extended with the addition of more leaves.

Natural Enemies

Encyrtid Wasp, Ageniaspis fuscicollis - wasp
Herpestomus brunnicornis -fly

Monitoring

Imported plants should be inspected to prevent spreading to other crops. Inspect leaves of the fruit for caterpillars and destroy them. On the plant, look for ovular shaped eggs near the bud of the apple tree. Tents can be found in the crown area for trees so it is important to closely monitor this section. The only time cocoons will not be present is when the apple tree is dormant, from late winter to early spring.

Action Threshold

When tents are limited in numbers physical controls can be used to effectively manage the pest. Higher populations will need to be assessed for chemical control needs.

Physical/Mechanical Controls

Inspection of apple imports is an effective method to reduce spreading to local crops. A means of physical control is removing tents from trees and destroying eggs and larvae present.

Biological Controls

Introducing parasitoids or parasites can help reduce the amount of moth larvae. These species are taken from their native habitat in parts of Asia and Europe.

Some effective parasitoids include:

• Ageniaspis fuscicollis
• Herpestomus brunnicornis (fly).
• Dolichogenidea delecta (Haliday) (Braconidae)
• Ageniaspis fuscicollis (Dalman) (Encyrtidae)
• Herpestomus brunnicornis Grav. (Icheumonidae)
• Bessa paralella (Meigen)
• Zenillia dolosa (Meigen) (Tachinidae)
  
  

Chemical Controls

The bacterial insecticide Bacillus Thuringiensis (Bt) is an effective chemical control for Apple Ermine Moth. This product should be applied to leaves of the infected plants and is most effective when caterpillars first hatch. The insecticide kills the caterpillars as it feeds, particularly from May to June.

References

Antonelli, Arthur L. . "Apple Ermine Moth." Washington State University Insect Answers. August 1989. Washington State University . 4 Feb 2009 <http://cru.cahe.wsu.edu/CEPublications/eb1526/eb1526.html>.

"Yponomeuta malinellus (Zeller)* - Apple Ermine Moth." 11/13/2006. Canadian Food Inspection Agency. 4 Feb 2009 <http://www.inspection.gc.ca/english/plaveg/pestrava/ypomal/tech/ypomale.shtml>.

"Semiochemicals of Yponomeuta malinellus, the Apple ermine moth." The Pherobase. 10 Oct 2008. ISCA Technologies. 4 Feb 2009 <http://www.pherobase.com/database/species/species-Yponomeuta-malinellus.php>.

"APPLE ERMINE MOTH." Insect, Mites, and Related Pests. Government of British Columbia. 4 Feb 2009 <http://www.al.gov.bc.ca/ornamentals/publications/pesticide/insect/APPLE_ERMINE_MOTH.pdf>.

Lee, Jang-Hoon. "Larval Parasitoids of the Apple Ermine Moth Yponomeuta malinellus ZELL,. (LEPIDOPTERA Yponomeutidae) in Korea, Japan, and China." Agricultural Research Service. 02 Apr 2009. United States Department of Agriculture. 5 Feb 2009 <http://www.ars.usda.gov/research/publications/publications.htm?seq_no_115=159071>.

LaGasa, Eric . "Orchard Pest Management Online." Apple Ermine Moth. 2009. Washington State University . 6 Feb 2009 <http://jenny.tfrec.wsu.edu/opm/displaySpecies.php?pn=620>.

Flint, Mary Louise. Pests of the Garden and Small Farm: A Grower's Guide to Using Less Pesticide. Oakland, Calif.: UC Division of Agriculture and Natural Resources, 1998.