Emerald Ash Borer Continues to Spread...What Do I Do?



Emerald Ash Borer Decision Guide for
 Urban and Community Trees

Our struggles to manage the forest in the face of invasive exotics continue to cause us problems.  Emerald ash borer (EAB) is spreading and will continue to spread as long as host trees are available.  I received word last week that the insect has been positively identified on the Penn State campus in an ash research plantation, in Musser Gap on the Rothrock State Forest by DCNR foresters, and by the Penn State Forestland Management office on the Stone Valley Experimental Forest in Huntingdon County.

Knowing this I think we would have to make the assumption that all stands with high densities of ash trees are under an immediate threat of attack in the Centre Region.  In other areas where populations of EAB are still more geographically isolated it is recommended to use mapping as your guidance for management prescriptions. EAB populations expand at an average rate of ½ mile per year.  Stands greater than 5 miles from EAB populations are projected to be about 10 years away from EAB impacts. Unfortunately, confidence in maps of EAB population locations is low and only serves as a guideline.

Insecticide controls are avaialble for individual ash trees and trees in urban/suburban settings.  Purdue University has done a great job at pulling this information together.  You can find their information here.  Their suggestion for making management decisions is as follows: If EAB has been found in your county or within 15 miles, you should start protecting your ash trees.

Also, recall that in April of 2011 the quarantine restricting the in-state movement of all ash materials and hardwood firewood was lifted by the PA Department of Agriculture.  To my knowledge, the federal quarantine has remained in effect to help stop the spread into other states.

Below are silvicultural guidelines that were developed by the Michigan DNR you may find them helpful in making management desicisions.

Ash resources within 10 miles of EAB populations:

These stands are at high risk of EAB caused ash decline and mortality within 10 years. Reduce ash basal area, if ash comprises greater than 10% of total stand basal area. If the ash resource is of poor vigor, the risk of EAB caused decline and mortality is greater. Where ash resources are generally of poor vigor, retain a minimal or no ash component.

Ash trees in upland hardwoods: Generally, it is not advisable to reduce stand basal area below 70 square feet per acre. Remove the largest ash first, leaving vigorous pole sized trees.  Limit canopy gaps to 60 feet in diameter or less if possible.

Ash resources > 10 miles of EAB populations:
These stands may have greater than 10 years before EAB arrives. Use conventional forest management practices to increase tree species diversity and decrease ash components, as outlined above. Ash reduction is a higher priority the nearer an ash resource is to EAB populations. (Note: Watch for newly discovered EAB populations established via artificial movement of firewood or other ash products which place stands < 10 miles for EAB populations.)

Tree species diversity and stand regeneration: The EAB mortality or ash pre-salvage/salvage harvests may lead to under-stocking, conversion to undesirable tree species and/or to areas of non-forest cover. This is especially true where American beech and ash comprise a significant proportion of the total stand basal area. In such cases, active treatment of ash regeneration through cutting and/or herbicide application may be necessary to keep the ash component to an appropriate level and to encourage tree species diversity. Under-planting and/or planting canopy openings may be necessary to attain the desired stocking and mix of tree species. Select tree species which are matched to the habitat type and which improve species diversity.