NDSU Extension - Griggs County

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June 1

The Extension Connection

By Megan Vig

Emerald Ash Borer (EAB) is moving closer to our county.  This highly destructive pest attacks only species of ash trees (Fraxinus spp.).  The larvae feed under the bark, disrupting the movement of water and nutrients, and kills ash trees within several years.  EAB has killed hundreds of millions of ash trees in the United States over the past decade.  Though it has not yet been found in North Dakota, EAB has been found in Minnesota and South Dakota, as well as to the north of us in Manitoba. 

Reported by the North Dakota Department of Agriculture, North Dakota has more than 90 million ash trees.  Based on tree inventories in 95 North Dakota communities, ash trees make up between 20 to 80 percent of trees along streets and in city parks.  They are also found in rural plantings and native forest areas.

The vast majority of damage comes from feeding by the larvae in the phloem tissue, just under the bark.  EAB larval galleries also can extend into the sapwood.  This feeding behavior damages the vascular system of the tree, blocking water and nutrient transport. Visible symptoms of damage are dieback of the tree crown and excessive sprouting (epicormics branches) along the main stem of the tree.  However, these symptoms are unlikely to be seen during the first year of infestation.  Instead, dieback probably will be observed only in trees that have been infested for three years or longer.  Keep in mind that environmental stress and diseases, such as ash yellows, commonly are responsible for symptoms similar to EAB infestation.  Woodpeckers are attracted to EAB-infested trees, and excessive pecking damage by woodpeckers may be another visible symptom of EAB presence.

One of the main cultural methods for preventing the spread of EAB is not moving infested firewood, logs or nursery stock to uninfested areas.  Much of the rapid spread of EAB outside of its original detection sites near Detroit, Michigan, was due to direct, human-assisted movement of these products.  Larvae of EAB are hidden underneath the bark of living trees or boards cut from infested logs where they can be transported easily into non-EAB-infested areas.  Another cultural control method is timely removal of EAB-infested trees and then chipping the trees to a small size, less than 1 inch, or burning the trees that were removed.  This will kill EAB and help prevent further spread.  Many cities are proactively removing and replacing diseased or unhealthy ash trees.  This have been done to increase diversity of tree species with new plantings to prepare for the arrival of EAB. 

If you are interested in learning more about EAB, there are two new publications available.  Call the Extension Office at 797-3312 to reserve a copy of E1634 Emerald Ash Borer Biology and Integrated Pest Management in North Dakota and/or E1604 Insects Frequently Confused with Emerald Ash Borer in North Dakota.

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