Emerald Ash Borer

Emerald Ash Borer (EAB) is an invasive pest that kills ash trees and was declared a nuisance by the City of Oakdale in 2010. Ash trees infected with EAB become weak and pose a danger to people and property. It can take several years for ash trees to show signs and/or symptoms of EAB infestation. A tree can appear healthy but may still be infested. It is important to identify ash trees, take steps to prevent the spread of EAB, and remove infested trees. 

Ash Tree Identification

There are three types of ash trees in Minnesota - black, green and white. Four keys to identifying ash trees include

  • Branches that grow directly across from one another;
  • Compound leaves with five to many leaflets;
  • Diamond-shaped bark pattern;
  • And paddle-shaped seeds that hang in clusters. 

Signs and Symptoms of EAB Infestation

  • Canopy dieback: Leaves on the top or one part of the tree start dying which can eventually affect the whole tree
  • Shoot growth: Sprouts of leaves growing from the tree base signal stress on the tree
  • Woodpecker activity: Holes from woodpeckers indicate birds pecking to eat EAB larvae under the bark
  • Blonding of bark: Bark looks lighter due to woodpeckers stripping the bark to get to the larvae
  • Cracks in bark or chunks falling off: Larvae tunneling underneath the bark can cause it to split or fall off
  • Serpentine pattern: Larvae make squiggly, s-shaped patterns under the bark
  • D-shaped exit holes: Adult beetles leave small, d-shaped holes when they exit ash trees

Treatment and Solutions

  • Treat your tree: Non-infected trees can be treated with pesticides. Treatment is less expensive than removal and needs to be repeated every few years. Treating a tree doesn’t guarantee survival of the tree but can help extend tree life. It’s important to get an evaluation of your tree to see if it can be treated. 
  • Remove the tree: If the tree is badly infested or treatment doesn’t work, it will need to be removed.
  • Replant a new tree: After removing an infested tree, consider replanting a new one. The City of Oakdale gives away 200 free trees each April in honor of Arbor Day.