Summary

Defoliating moths are moths whose larvae feed on leaves and needles of plants.
Defoliation damages trees by removing or damaging the leaves, the photosynthesizing parts of the trees.
Defoliation usually causes little harm to trees but can be devastating under outbreak conditions.
Invasive defoliating moths are a threat to Alaska’s forests because:
- They lack natural enemies
- Are able to exploit resources
- They have known pathways for introduction
Signs and symptoms of defoliating moths include:
- Loss of foliage from the trees
- Presence of any life stage of the insect
- Reduced or stunted growth
- Branch dieback
Invasive moths can reach Alaska through:
- Infested shipping containers
- Live plants for the plant trade
- Items being shipped from infested areas that have been stored outdoors near lights prior to shipping
Defoliating moth threats to Alaska include:
- Asian and European spongy moth
- Nun moth
- Rosy moth
- Siberian silk moth

Large-scale defoliation events are rare, but when observed should be noted and reported to Cooperative Extension, the Alaska Division of Forestry or the US Forest Service so they can be investigated further.

Vocabulary

Deciduous: refers to trees or shrubs that lose their leaves annually, usually in the fall
Defoliating moth: A moth whose larvae feed on the leaves or needles of trees and shrubs.
Caterpillar: Common term for the immature stage of a moth or butterfly,
Frass: Insect excrement
Galls: Abnormal growth of plant tissue
Larvae: immature stage of some insects.
Chlorophyll: the green pigment in plants that is responsible for the absorption of light, contributing to photosynthesis.
Photosynthesis: the process used by plants to convert light from the sun to energy that can be used by the plant.
Polyphagous: able to feed on a variety of food sources.
Signs: physical evidence of a pest.
Symptoms: a plant’s response to a pest.
Pathway: the means and routes by which invasive species are imported or introduced into new environments.

Sources and more information

Furniss, R. L. and V. M. Carolin. 1977. Western Forest Insect. USDA Forest Service Misc. Pub. 1339, 654 pp.
Dreistadt, S. H. 2004. Pests of Landscape Trees and Shrubs: An Integrated Pest Management Guide. Publication #3359, ANR Publications, University of California, 6701 San Pablo Avenue, Oakland, CA 94608-1239. 501pp.
Holsten, E., P. Hennon, L. Trummer, J. Kruse, M. Schultz, and J. Lundquist. 2009. Insects and Diseases of Alaskan Forests. USDA Forest Service, Alaska Region R10-TP-140, 246 pp.
Introduction to Defoliating Insects. 2011. U. S. Forest Service – Forest Health Protection – Rocky Mountain Region.
McManus, M. L., D. R. Houston, and W. E. Wallner. 1979. Gypsy moth handbook. The homeowner and the gypsy moth: guidelines for control. USDA Combined Forest Pest Research and Development Program. Home and Garden Bulletin. 001-000-03950-4.
Molet, T. 2012. CPHST Pest Datasheet for Dendrolimus sibiricus. USDA-APHIS-PPQ-CPHST.
Molet, T. 2012. CPHST Pest Datasheet for Lymantria dispar asiatica. USDA-APHIS-PPQ-CPHST.
Molet, T. 2012. CPHST Pest Datasheet for Lymantria mathura. USDA-APHIS-PPQ-CPHST.
Molet, T. 2012. CPHST Pest Datasheet for Lymantria monacha. USDA-APHIS-PPQ-CPHST.