By Scout Nelson
Emerald ash borer (EAB) is now a growing concern for North Dakota communities, farms and homeowners. The invasive insect damages ash trees by feeding under the bark and blocking the tree’s flow of water and nutrients.
Joe Zeleznik, NDSU Extension Forester, explained the issue through key numbers that show the size of the threat and help people make better decisions. His message is simple: “You can’t manage it if you can’t measure it.” The goal is to understand where EAB is found, how quickly it can spread, and when tree treatments make sense.
Three North Dakota counties currently have known EAB infestations. The first confirmed find occurred in LaMoure County in August 2024. No new infestations were found during 2025, but Cass and Burleigh counties reported finds in 2026. These discoveries show that the pest is moving into new areas.
North Dakota has an estimated 90 million ash trees. They grow in native forests, shelterbelts and urban forests. This large number shows why EAB creates a major challenge for tree owners and communities. Losing ash trees can change neighborhoods and increase removal and replacement costs.
Bismarck provides an example of how planning can reduce future problems. Ash trees currently make up about 22% of the city’s boulevard ash population. In 2008, ash made up 36% of the city’s urban forest. Since then, the city forestry department has removed ash trees that are in poor condition or poor locations and has worked to create a more diverse urban forest.
Some North Dakota communities have much higher levels of ash. Ash can make up as much as 80% of boulevard trees in some communities. If EAB reaches these areas, removing and replacing large numbers of trees can be expensive. Communities can reduce future risk by planting a wider mix of tree species. The ND Tip Tool from the North Dakota Forest Service can help residents learn more about local urban forests.
The North Dakota Legislature has allocated $950,000 for communities preparing for the pest. The North Dakota Forest Service distributes these funds through a grant program. Future funding for these efforts is not certain, making local planning important.
The North Dakota Department of Agriculture places more than 250 EAB traps across the state each year. Traps have been used since 2008 in high-risk areas, including campgrounds, rest areas, and large rail yards.
EAB normally moves only about one to two miles each year without human help. However, people can move the insect much farther by transporting firewood and wood packing materials. Residents should follow quarantine rules and avoid moving firewood from areas where EAB is present.
Moving firewood out of a quarantined county can result in a $5,000 fine. Quarantines are established by the North Dakota Department of Agriculture. Residents can check the state’s EAB information and quarantine map before moving firewood.
Tree owners also need to understand treatment timing. Injections containing emamectin benzoate can protect healthy or lightly affected ash trees from EAB for about two to three years. Treatment is usually done by a trained professional. Treatment can be expensive, but it can preserve valuable trees.
Tree conditions are also important. An ash tree with approximately 40% canopy dieback is generally considered near the upper limit for responding to emamectin benzoate injections when deciding whether to treat or remove an ash tree. This is an estimate, and some trees may not recover even with timely treatment.
Treatment is generally recommended when EAB has been found within 15 miles of an ash tree. Treating trees too early can waste money because the pest may still be many years away. EAB may take 10 years or longer to arrive.
The presence of EAB means North Dakota communities need to plan ahead. Homeowners, farmers and local leaders can identify ash trees, watch for signs of infestation, follow quarantine rules and consider tree diversity before major losses occur.
Photo Credit: istock-pyzata
Categories: North Dakota, General