Cankerworms Defoliate Trees in So. Md.

LEONARDTOWN, 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

Source: Maryland Department of Natural Resources

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