Residents in Southern Maryland may have noticed the leaves on their trees being eaten by “inch worm” type caterpillars shortly after they leafed out this spring. The spring cankerworm is a native caterpillar that normally occurs in smaller populations. This year the amount of defoliation caused by the canker worm is widespread in St. Mary’s County.
Mark Muir a forester with the DNR Forest Service states that it is possible that the mild winter weather may be responsible for the canker worm’s higher than normal population. Because the defoliation occurs in early spring, most healthy trees will refoliate and survive. A Healthy tree can normally withstand a single early spring defoliation. Trees that are in a “stressed” condition are more susceptible to mortality after being defoliated. Conditions such as soil compaction, drought, and inadequate sunlight and water due to competition from other trees can cause a tree to be stressed.
Since the spring cankerworm is a native insect not known for heavy defoliation, there are no programs or plans to spray chemicals to control its numbers. While uncommon, it is not unheard of for populations of native insect populations to spike due to weather patterns or other environmental conditions.
Mark Muir also states, one way to prevent the spread of destructive forest pests is not to move firewood in or out of your local area. Regardless, if firewood is for camping or to heat your home, transporting it in or out of your local area can spread forest pests and their eggs.
For more information on forest pest management go to the Maryland Department of agriculture website at www.mda.state.md.us/plants-pests/. For more information on forest management go to the DNR Forest Service website at www.dnr.maryland.gov/forests/.
