Crop & Pest Report


| Share

Emerald Ash Borer a Giant Leap Closer to North Dakota (05/03/18)

The Canadian Food Inspection Agency (CFIA) confirmed emerald ash borer (EAB) in Winnipeg, Manitoba in December 2017.

Emerald Ash Borer a Giant Leap Closer to North Dakota

The Canadian Food Inspection Agency (CFIA) confirmed emerald ash borer (EAB) in Winnipeg, Manitoba in December 2017. Only sixty miles north along a well-travelled highway, it is the closest known EAB infestation to North Dakota. The insect appears to have arrived at least five years before its discovery. In that time, EAB spread to adjacent street trees and to park trees 1,500 feet away. Surveyors discovered that the best indicator of an EAB infestation is observing light colored bark caused by woodpeckers foraging on ash trees for EAB larvae.

l.johnson EAB

EAB is a small metallic green beetle. Adult beetles lay eggs on ash tree bark during the growing season. When the eggs hatch, the larvae chew tunnels under the bark, cutting off the flow of water and nutrients and stressing ash trees. The stressed tree attracts more beetles which continue the attack until they kill the tree. North Dakota is particularly vulnerable to EAB because green ash is our most abundant tree in forests, in windbreaks, in conservation plantings, and in communities.

EAB cold-hardiness research, cross-referenced with a study of actual temperatures of ash tree inner bark, accurately predicted that EAB would survive these conditions. EAB survival in Winnipeg’s cold winters is associated with thick trunks, south sides of trees, and being below the snow line. It is reasonable to expect that EAB will be able to survive North Dakota winters as well.

Based on cold-hardiness research, EAB is likely to spread more slowly in Winnipeg (and in North Dakota once it arrives) than it has elsewhere. Once detected, EAB cannot be eradicated, so Winnipeg is adopting the “Slowing Ash Mortality” (SLAM) approach to municipal tree management. This approach is based on a good tree inventory and involves selectively removing large ash trees, removing most ash trees as they die, treating some ash trees with pesticide to delay their death, and intensively surveying and monitoring the infestation.

Lessons learned from Winnipeg: Cold will not protect North Dakota from EAB. Managing EAB is expensive. Do not plant ash. Plant a variety of trees. Update or begin a tree inventory. Remove poor quality ash trees. Develop an EAB management plan. Survey for EAB and infested trees. Learn more about emerald ash borer

Green ash trees all across the state already show symptoms of stress from many causes. This makes it very difficult to monitor them for EAB. In order to identify an infestation as early as possible, be alert to woodpecker feeding in ash trees – especially on the south sides of ash trunks and branches. Learn more about EAB at:

l.johnson.EAB on penny


Lezlee Johnson

North Dakota Forest Service

Forest Health Manager

This site is supported in part by the Crop Protection and Pest Management Program [grant no. 2017-70006-27144/accession 1013592] from the USDA National Institute of Food and Agriculture. Any opinions, findings, conclusions, or recommendations expressed are those of the website author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.

USDA logo

Creative Commons License
Feel free to use and share this content, but please do so under the conditions of our Creative Commons license and our Rules for Use. Thanks.