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Maryland Department of Agriculture

Emerald Ash Borer Monitoring & Suppression

About the emerald ash borer

The emerald ash borer (EAB) is an exotic pest of ash trees. It is native to Asia and thought to have arrived in the United States in solid wood packing material from its native Asia. It was first detected in the Detroit, Michigan/Windsor, Ontario area in July 2002. 

The threat to ash trees

Because of EAB, millions of ash trees have died in the central and northeastern United States. USDA estimates that at the national level, if the Emerald Ash Borer went unchecked in the lower 48 states, the undiscounted loss could range from $20 - $60 billion dollars. Many consider it far more serious than spongy moth, and perhaps equal to the chestnut blight.

Economic impact in Maryland

The greenhouse and nursery industry is the second largest agricultural sector in Maryland. It accounts for $1.96 billion in gross receipts. (Source: Agriculture in Maryland Summary 2010 - USDA National Agricultural Statistics Service).

  • Ash trees are one of the most common landscaping trees used in the U.S. and are common in western Maryland forests.
  • Ash wood is used for all traditional applications of hardwood from flooring and cabinets to baseball bats and tool handles.
  • Ash is the most common tree in Baltimore - 293,000 trees, 10.4% of trees total population.
  • Ash accounts for 5,982,000 to 6,591,000 trees in the Baltimore metro area. USDA has estimated losses could exceed $227,568,000 in the Baltimore area alone.

*Galvin citing DNR, MDA, and USDA sources 2003.*

EAB monitoring & control in Maryland

The Maryland Department of Agriculture in cooperation with the U.S. Forest Service and the Department of Natural Resources has conducted several programs to monitor and suppress EAB as well as release biological control agents. 

Monitoring

MDA has been active with placement of both prism and funnel traps to detect EAB in areas where it has not been found. The most common of these were the purple prism traps that were used statewide for many years.  As the infestation has spread, early detection trapping has been scaled back. Currently MDA is only trapping on the Eastern Shore to find newly infested counties. 

Suppression

EAB larvae can be successfully suppressed by the use of various systemic insecticides. Treatments can be made by direct trunk injection or soil injection. Since it is done on a tree by tree basis, only trees of high value or importance are economically practical to treat. MDA working with DNR did treatments to ash trees located in several State and Municipal Parks in 2016. Additional trees will be treated in the upcoming years.  Trees will be monitored and retreated every 2 to 3 years as needed. 

Biological control agents

The MDA in cooperation with the USFS has been releasing several biological control agents in an attempt to help with long term management of EAB.  Parasitoids that attack both the eggs and larvae of the EAB have been released at selected sites in State and Municipal parks. Sites will be monitored to check for the establishment of the parasitoids.  Several of the parasitoids have been shown to establish in MD from past releases. The parasitoids do best in forested area that consist of 25% ash or greater so are not recommended for use in urban areas. 

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