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Cankerworms Defoliate Trees in Southern Maryland

Photo of Spring CankerwormLeonardtown, Md. (May 10, 2012) ─ Residents in Southern Maryland may have noticed that inchworm-like creatures have wasted no time feasting on the area’s foliage since they appeared in early spring. With this year’s higher populations, the cankerworm has devoured tree leaves throughout Charles and St. Mary’s Counties. The worms are now finished their destructive caterpillar cycle and have returned to the ground to pupate.

“It is possible that the mild winter weather may be responsible for the spring cankerworm’s higher than normal population,” said Mark Muir, of the Maryland Department of Natural Resources (DNR) Forest Service. “Because the defoliation occurred in early spring, most healthy trees will refoliate and survive.”

A healthy tree can normally withstand a single, early spring defoliation. A tree that is in a stressed condition is more susceptible to mortality after its leaves have been eaten. Conditions such as compacted soil, drought, as well as inadequate sunlight and water can cause a tree to be stressed.

The spring cankerworm is a native insect not known for heavy defoliation, so there are no programs or plans to spray chemicals to control its numbers. While uncommon, native insect populations can spike due to weather patterns or other environmental conditions.

To prevent the spread of destructive forest pests and their eggs, do not move firewood from its location.

More information on forest pest management is available through the Maryland Department of Agriculture’s at  or DNR at

   May 10, 2012

Contact: Josh Davidsburg
410-260-8002 office I 410-507-7526 cell

The Maryland Department of Natural Resources is the state agency responsible for providing natural and living resource-related services to citizens and visitors. DNR manages nearly one-half million acres of public lands and 17,000 miles of waterways, along with Maryland's forests, fisheries and wildlife for maximum environmental, economic and quality of life benefits. A national leader in land conservation, DNR-managed parks and natural, historic and cultural resources attract 11 million visitors annually. DNR is the lead agency in Maryland's effort to restore the Chesapeake Bay, the state's number one environmental priority. DNR is the lead agency in Maryland's effort to restore the Chesapeake Bay, the state's number one environmental priority. Learn more at