Emerald ash borer detected north of Mapleton in second Cass County find

BISMARCK, N.D. (Valley News Live) - State forestry officials have detected emerald ash borer north of Mapleton, marking the second finding in Cass County and raising new concerns about the spread of the destructive insect across North Dakota.

North Dakota Forest Service staff confirmed the detection this week. The site is more than 12 miles from the first Cass County detection, an insect larva found in the city of Fargo by city forestry staff in January. This suggests the pest may be spreading more widely than previously known.

Emerald ash borer was first found in North Dakota in LaMoure County in August 2024. The Fargo detection in January was the second confirmed case in the state and the first in Cass County, prompted in part by the insect’s detection in nearby Moorhead, Minnesota, in 2023.

“While this detection is unfortunate, it is not unexpected,” Agriculture Commissioner Doug Goehring said. “Landowners should be diligent in monitoring ash trees in shelterbelts and other rural areas for indicators of emerald ash borer and report any suspect infestations.”

What Is Emerald Ash Borer?

Emerald ash borer is a wood-boring insect native to Asia that was first detected in the United States in 2002. It has since spread to 37 states and killed hundreds of millions of ash trees.

The insect typically does not fly more than a mile or two on its own, but it can travel long distances when people move firewood, tree trimmings, or ash nursery stock.

North Dakota has more than 90 million ash trees in native and rural forests. Ash trees make up between 20% and 80% of trees along city streets and in parks statewide. Without treatment, infested trees can die within a few years.

Signs of Infestation

Residents should watch for the following indicators:

• Canopy thinning
• Leafy sprouts shooting from the trunk or main branches
• S-shaped galleries under the bark
• Bark splitting
• Woodpecker damage
• D-shaped exit holes

What Happens Next

The North Dakota Department of Agriculture and its partners will scout near the detection site to determine how the pest arrived and how far it may have spread.

Treatments are not recommended until emerald ash borer is detected within 15 miles of a location. Residents who choose to treat their ash trees are strongly urged to hire a reputable tree service company with a certified applicator. Most treatment options are restricted use and can only be applied by a licensed tree care professional.

Quarantine Restrictions in Effect

The NDDA maintains a quarantine restricting the movement of regulated commodities from infested areas. Cass County is already within the quarantine zone.

Regulated materials include:

• All hardwood firewood
• Ash logs and branches
• Nursery stock
• Wood chips

Moving regulated materials from a quarantined area to a non-quarantined area without a permit can result in civil penalties of up to $5,000.