Out
On A Limb / April 2007
Forest Feeder
The gypsy moth is one of North America’s most devastating forest pests. Although the species originally evolved in Europe and Asia and existed there thousands of years, it was accidentally introduced near Boston around 1868. By 1890 the State and Federal Government began attempts to eradicate the gypsy moth but failed. The range of gypsy moth has continued to spread south and west at approximately 5-10 miles per year. In the last 10 years, it has reached 23 counties in West Virginia.
Gypsy moth was first detected in West Virginia in 1972. In 1978, the West Virginia Department of Agriculture (WVDA) made its first discovery of caterpillars, and defoliation was first observed and recorded in 1985. The continued progression of gypsy moth in West Virginia is marked by a trend of expansion from northeast to southwest. Defoliation occurred on 345,340 acres in 1990. In 2000, it was 322,892 acres. But the highest level to date was in 2001 when 603,630 acres were defoliated.
Gypsy moth populations peak every 8 to 11 years.
Gypsy moths feed on the foliage of more than 500 different trees and shrubs, though its most common hosts are oaks and aspen. They attack trees by feeding on their leaves. Severe defoliation and mortality are most likely in stands having a high percentage of oak, the favorite food of gypsy moth caterpillars.
Repeated heavy defoliation by gypsy moths leads to the death of trees. Spruce, pine and hemlocks die after one heavy defoliation. After two successive years of defoliation, hardwood tree mortality can reach as high as 80%.
75 million acres have been defoliated by gypsy moth since 1970.
Gypsy moth populations are typically eruptive and in any forest stand, densities may fluctuate. When densities reach very high levels, trees become completely defoliated. Several successive years of defoliation, along with contributions by other factors like drought, ice storms, and other insect pests, result in tree mortality.
The financial impact is staggering. Considering the losses are valued at over $300 an acre, it ranges in the millions.
Another major concern is the potential loss of economically critical and ecologically dominant oak species.
The gypsy moth is potentially the most destructive forest pest threatening West Virginia woodlands.
The West Virginia Department of Agriculture (WVDA) coordinates and conducts a cooperative regional suppression program between landowners. Aerial spraying is done on a demand basis to minimize forest damage. Spraying must be done in May to early June when the caterpillars are small.
Ohio will spray 180,000 acres in 20 counties this spring–more than twice the amount of land dusted last year–to stop the spread of the gypsy moth. The pest that has destroyed tens of thousands of trees in Ohio and this will be one of the largest sprays since the state began the program in the 1970’s. Experts say recent dry springs, as well as mild winters, have caused the moths to reproduce rapidly.
Ten states along the leading edge of gypsy moth populations, in cooperation with the USDA Forest Service, have implemented a region-wide strategy to minimize the rate at which gypsy moth spreads into uninfested areas. The spread has been reduced from the historical high level of 13 miles per year to 3 miles per year. Still, every year, isolated populations are discovered beyond the contiguous range of the gypsy moth and despite everyone’s best efforts, it seems inevitable that gypsy moths will continue to expand their range in the future.
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