University of Maryland to Study Emerald Ash Borer with Rockville’s Help

Rockville’s forestry staff will help the University of Maryland conduct a study on the effects of parasites on the emerald ash borer, an invasive insect pest that is devastating ash trees across the eastern United States.

Ash borer infestation is peaking in Rockville, requiring that hundreds of ash trees be removed from the city’s parks, streets and private property. About 3 percent of the city’s street-tree population is ash, with an unknown number of the trees in the city’s forested park areas.

For the study, trees infested with borer larva will be removed and cut into sections that will be studied in UMD labs. When the adult emerald ash borer beetles emerge from the tree sections in spring, UMD researchers will release parasites into the controlled environment to determine if they’re capable of controlling the invasive insect. If the research is successful, parasites could be released into the environment as a natural means to reduce the ash borer population.

In the meantime, residents should be aware that ash trees on their properties should be monitored for signs of emerald ash borer. Effective chemical treatments exist, but must be applied before the tree shows signs of infestation.

The emerald ash borer is a non-native, wood-boring beetle that is specific to ash trees and has killed tens of millions of trees nationwide. The pest feeds on the tree’s vascular system throughout the summer and fall, disrupting the movement of water and nutrients within the tree and eventually killing it. The insect, native to China, leaves a unique “D”-shaped exit hole in ash trees that distinguishes it from native borer species. Once a significant infestation is identified, treatment options have proven ineffective in saving trees. Once an ash dies, the tree degrades quickly and can become a danger to people and property.

For more information on the emerald ash borer and how to identify ash trees, visit For more information, contact City Forester Wayne Noll at 240-314-8700 or