BirdCast: Garden Pests: Gypsy Moths

Pest: Gypsy Moth (Lymantria dispar).

Discussion: Adult males are dark gray flying moths less than an inch in size; females are off white, flightless and about 1 inch long. Larval caterpillar stages are hairy, about 2 inches long and with blue (5 pair) and red (6 pair) dots along the back. Eggs are layed under a fuzzy yellow cover, and can be found on bark and a variety of other surfaces such as outdoor walls or on a car bumper/trailer. Gypsy moth caterpillars feed on leaves (on both coniferous and deciduous trees). Large outbreaks, which occur in 2-4 year periods, can lead to serious defoliation and the death of many trees. During large gypsy moth outbreaks, full grown caterpillars will be noticeable both in the foliage and on the ground under trees.

Gypsy moth caterpillars resemble, tent caterpillars another common backyard pest. Fully grown tent caterpillars do not have the same series of red and blue dots running along their back, and the hair covering their body is less bristly. Tent caterpillars can also be distinguished by the large silky webs they form between branches (Which, by the way, are easily controlled by pruning out these webs).

Pesticides Commonly Applied: Acephate (Orthene), Carbaryl (Sevin), Fluvalinate (Mavrik), Methoxychlor (Marlate).

Alternative Pesticides: Superior oil, pyrethrins, insecticidal soap.

Biological and Physical Controls: Use Bacillus thuringiensis kurstaki (BTK), a bacterium that can be sprayed on foliage to kill a number of pest caterpillars. You can also wrap a burlap strip (15 to 20 inches wide) around the trunk of your trees. Tie it in the middle of the strip, and let the top flap hang over the edge. Check for larval caterpillars "resting" in the burlap and destroy them regularly. As with other pests, you can also attract or introduce natural insect predators like tachinid flies, ground beetles or parasitic wasps/nematodes.

Bird Facts: Chickadees, Bluejays, nuthatches, Eastern Towhees, American Robins and other species of birds all dine on caterpillars and feed them to their young. Baltimore Orioles can eat up to 17 tent caterpillars a minute. In Manitoba, nesting density of Baltimore Orioles nearly doubled in the second year of a forest tent caterpillar outbreak.