Green cankerworm caterpillars infesting trees in Maryland are often mistaken for those of gypsy moth, says forest pest official, notes outbreaks generally follow three-year pattern with last outbreak in 2007 in Anne Arundel and Cecil Counties

Aimee Bellah

ANNAPOLIS, Maryland , May 19, 2014 (press release) – An infestation of cankerworms have eaten the leaves off of many trees in Calvert, Charles, St. Mary’s and Washington counties; however, entomologists with the Maryland Department of Agriculture (MDA) expect most trees to survive the defoliation without difficulty.

“These green caterpillars are often mistaken for the much more destructive gypsy moth,” said MDA Forest Pest Management Program Manager Bob Tatman, “Their presence, coupled with the obvious defoliation, has led some local residents to express concern about what’s going on. Trees experiencing defoliation due to cankerworms usually recover completely if they are not otherwise stressed.”

Cankerworms are native insects that have exhibited small sometimes three-year outbreaks around Maryland, the last one was in 2007 in Anne Arundel and Cecil Counties. The outbreaks are difficult to predict and more likely to be gone after the second year than to persist. Residents who are concerned about the cankerworm’s impact on high-value trees may want to consider insecticide treatment by a licensed pesticide applicator. In addition, watering and fertilizing may also help keep trees healthy.

For a list of licensed pesticide applicators near you, see: http://mda.maryland.gov/plants-pests/Pages/pesticide_db.aspx

To see the difference between gypsy moths and cankerworms, see: http://mda.maryland.gov/plants-pests/Pages/fall_and_spring_cankerworm.aspx

For more info on Maryland Forest Pest Management, see: http://mda.maryland.gov/plants-pests/Pages/forest_pest_management.aspx. Or call (410) 841-5922. 

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