General Questions and Answers
About Gypsy Moth

What is the gypsy moth?

The gypsy moth, Lymantria dispar, is one of North America's most devastating forest pests. The species originally evolved in Europe and Asia and has existed there for thousands of years. The gypsy moth is one of the major introduced pests of eastern North American hardwood forests. It is found mainly in the temperate regions of the world including central and southern Europe, northern Africa, central and southern Asia, and Japan. (See photos of damage)
 

Why is the gypsy moth a problem?
Gypsy moth caterpillars defoliate millions of acres of trees annually in North America. After mating, the females lay eggs in buff-coloured masses which contain 100 to 1,000 eggs. These are laid on the underside of tree limbs, bark, rocks and structures, including buildings, campers, mobile homes, etc.

How widespread is the gypsy moth in North America?  

Despite all control efforts since its introduction, the gypsy moth has persisted and extended its range. In the United States, the gypsy moth has rapidly moved north to Canada, west to Wisconsin, and south to North Carolina. Gypsy moth have been detected regularly in the western states and on the west coast of Canada but eradication efforts have prevented its establishment in western North America.
 

What is the status of the gypsy moth in Canada?

The gypsy moth is a regulated pest in North America. It is present, but managed in parts of Ontario, Quebec, New Brunswick and Nova Scotia. Due to eradication efforts undertaken by the federal and provincial governments, British Columbia has been considered officially free from gypsy moths from a regulatory perspective.

How does the gypsy moth spread from one area to another?

Gypsy moth caterpillars hatch from eggs during bud-breaking which occurs in mid-spring. Although the caterpillars are capable of feeding on over 500 species of trees and shrubs, they prefer broadleaved trees. The adult male and female gypsy moths are easily distinguished from one another; the males are brownish-grey, whereas the females are white with black markings and are slightly larger. The females mate and then lay eggs. Since the females are incapable of flight, the eggs may be laid on picnic tables, outdoor benches or in the cracks of a fallen tree. In many cases the eggs are laid in secluded spots to prevent predation by other animals. When someone inadvertently transports the egg masses on an outdoor article to a new un-infested area, the gypsy moth has lived up to its name.
 

What are the signs of a gypsy moth infestation?

During outbreaks in residential areas, gypsy moth caterpillars are an extreme nuisance. Trees lose their foliage, caterpillars crawl everywhere, and their droppings rain from the trees. When disease kills large numbers of caterpillars, as often occurs, the stench is overwhelming. In some cases, people develop an allergy to the hairs of the gypsy moth caterpillars. Repeated defoliation stresses trees and leads to their death.

How is the gypsy moth controlled?

Various control measures are available for use against the gypsy moth; however two commonly-used insecticides are Btk (Bacillus thuringiensis var. 'Kurstaki') and diflubenzuron or Dimilin. Btk is a naturally occurring bacterium that only kills caterpillars, and, Dimilin is a chemical that interferes with gypsy moth growth and eventually kills the caterpillar.  Only Btk is used for eradication programs in B.C.

For general information on aerial spraying, go to the Aerial Spray Frequently Asked Questions Page

Click here for more information on the biology of the gypsy moth.

Gypsy Moth Homepage

Contact Tim Ebata if you have comments on the presentation of this information.

BC Ministry of Forests and Range
Forest Practices Branch
P.O. Box 9513 Stn. Prov. Gov.
Victoria, BC
V8W 9C2

Section phone: (250) 387-8739
Section fax: (250) 387-2136