Emerald Ash Borer is an invasive beetle from Asia that infects and kills all native species of ash trees in North America. The larvae create tunnels under the bark as they feed. As these tunnels accumulate the ash tree begins to show signs of infestation. Once a tree shows symptoms of infestation it usually dies within 1-3 years.
Emerald Ash Borer was first found in North America in Michigan in 2002. Since then it has spread to numerous other states and Canadian provinces including Minnesota. In 2009, it was found in St. Paul and spread through the metro area. By 2016, the beetle had found its way to Duluth and most recently in 2019 it was found in 10 trees in Sauk Centre, MN.
With an estimated 1 billion ash trees throughout the state, emerald ash borer poses a substantial environmental and economic threat. EAB infestations are difficult to identify in the early stages and spread by both natural and artificial means; therefore, quarantines are enacted when an infestation is discovered. A map of the current EAB status can be found at the following website https://mnag.maps.arcgis.com/apps/webappviewer/index.html?id=63ebb977e2924d27b9ef0787ecedf6e9.
EAB’s active period is from May 1st to September 30th so it is best to avoid any removal or pruning of ash trees during this time. If you must prune or remove ash trees during this time due to health hazards have at least 1” of the outer bark and wood chipped onsite before transporting it to a removal site. It’s also important to not transport firewood to help control the spread of EAB. Landowners can also help control the spread of EAB by looking for systems of infestation.
Symptoms to look for include:
- Canopy thinning – branches will progressively start dying each year after infestation
- Increased woodpecker activity – these birds like to feed on the larvae, particularly downy and hairy woodpeckers
- D-shaped exit holes – the adults leave distinct D-shaped exit holes about 1/8” wide when they emerge from the tree
- Serpentine tunnels/bark splits – the larvae create meandering S-shaped tunnels as they feed on the vascular tissue of the tree which is only visible when the bark is peeled away. These tunnels can cause a split in the bark.
If you suspect one of your trees to have Emerald Ash Borer please call the Minnesota Department of Agriculture’s Arrest the Pest hotline at 888-545-6684. Also note the exact location of the tree and take a digital photo if possible. Landowners can also contact the local Pope County Ag Inspector- Barry Bouwman at 320-634-7791 or the Swift County Ag Inspector- Tom Orr at 320-843-4910.