Emerald Ash Borer EAB

Recognizing the warning signs early can significantly improve the chances of successful treatment.

1. D-Shaped Exit Holes

One of the most recognizable signs of Emerald Ash Borer activity is the appearance of tiny D-shaped holes in the bark. These holes are left behind when adult beetles emerge from the tree between May and August.

2. Galleries Under the Bark

Larval feeding creates winding S-shaped galleries beneath the bark. These tunnels interrupt the tree’s ability to transport water and nutrients.

3. Bark Splitting

As galleries expand, the bark may begin to crack or split vertically, exposing the tunnels underneath.

4. Canopy Dieback

Branches in the upper canopy begin to lose leaves and die. This symptom often becomes more noticeable each year as the infestation progresses.

5. Epicormic Sprouting (Suckers)

The tree may attempt to survive by producing shoots, or suckers, near the trunk base or lower branches.

6. Increased Woodpecker Activity

Woodpeckers are among the primary predators of Emerald Ash Borer larvae in North America. An unusual increase in woodpecker feeding activity can indicate an infestation.

7. Presence of Adult Beetles

Adult Emerald Ash Borers are bright metallic green and slightly smaller than a dime. Their appearance near an ash tree should prompt immediate inspection by a certified arborist.

Minnesota is one of the states hardest hit by the Emerald Ash Borer because it has one of the largest ash tree populations in the United States, with an estimated one billion ash trees growing in forests, neighborhoods, parks, and along city streets. Since the insect was first discovered in St. Paul in 2009, it has spread rapidly across the state and has now been confirmed in dozens of counties. The impact has been especially severe in the Twin Cities Metro area, where ash trees once made up a significant portion of the urban tree canopy. St. Paul was the first Minnesota city to detect Emerald Ash Borer and remains one of the most heavily affected communities.

City officials describe the situation as critical, with the pest now established throughout the city and thousands of ash trees on private property either infested or at risk. Minneapolis has experienced similar losses, having removed tens of thousands of public ash trees as part of a long-term management program. Other Twin Cities communities with widespread Emerald Ash Borer activity include Shoreview, Woodbury, Maplewood, Roseville, White Bear Lake, Oakdale, Arden Hills, North Oaks, Vadnais Heights, Mahtomedi, Hugo, Forest Lake, and many other cities throughout Ramsey, Hennepin, and Washington counties.

 In some neighborhoods, residents have watched entire rows of mature ash trees disappear within a decade. Beyond the visual loss, the economic impact has been substantial, with municipalities spending millions of dollars on tree removal, replacement, and treatment programs. Environmental consequences are also significant. Ash trees provide shade that lowers summer temperatures, improves air quality, reduces stormwater runoff, and supports wildlife habitat. As these trees die, homeowners often face expensive removal costs, while communities lose valuable canopy cover that can take decades to replace.

Arborists across the Twin Cities continue to encourage early detection and treatment because healthy ash trees can often be preserved if Emerald Ash Borer is identified before extensive canopy decline occurs. For many Minnesota communities, the fight against Emerald Ash Borer is no longer about preventing its arrival—it is about managing its long-term impact and preserving as many healthy ash trees as possible for future generations.

The statements about St. Paul being the first Minnesota detection, the statewide scale of the infestation, and the critical situation in the Twin Cities are supported by the Minnesota Department of Agriculture, Minnesota DNR, and the City of St. Paul. (stpaul.gov)