Forty-one DNR forestry staff from across the state took to the streets and parks of Burlington Wednesday to assess the health of 900 publically owned ash trees. Trees were studied for evidence of emerald ash borer (EAB), which has been discovered in ash trees in three eastern Iowa locations: an island in the Mississippi River in Allamakee County in 2010, in Burlington, and most recently, Fairfield.
“Burlington is the largest city that has EAB evidence in its urban forest. Having a city forester on staff and a tree inventory in existence helps city officials set priorities.” said Tivon Feeley, DNR Forest Health Program Leader. “DNR forestry staff came here to see firsthand the symptoms of the presence of EAB in trees and to help city staff determine priority trees to remove, trees that are candidate trees for treatment, and trees that can wait until additional funds for removal are available.”
The day began with hands-on training. DNR forestry staffs were provided tools and instructed how to find EAB larva in a 4 in. - 6 in. diameter limb from an infested tree. Symptoms include evidence that woodpeckers ― probably Downey woodpeckers in Burlington ― leave scrape marks where they’ve sought the larva under the bark. Quite small “D”-shaped holes reveal where larvae have exited the tree (D-shaped because the bottom of the EAB larva is flat and the top surface is rounded). Cracking in the bark along a branch, and yellowing and thinning of the tree’s crown are other symptoms.
These symptoms are shared with other ash tree diseases, so the presence of EAB larva or adult beetles is the only sure confirmation. Adding to the difficulty of determining if a tree is infested is that bark sometimes heals over the symptoms. A tree could look healthy for anywhere from two to seven years before an EAB infestation is obvious.
“In five to seven years, most ― if not all ― of the ash trees in Burlington will die from infestation of EAB,” said Feeley. “Residential landowners that have ash trees should begin planting replacement tree species now. That way the new trees get a few years’ growth before currently large, healthy appearing ash trees succumb to EAB.”
“Cities without foresters on staff may call the DNR to assist them with making a tree inventory, so they know where and how many publically-owned ash trees they have,” says Paul Tauke, DNR Forestry Bureau Chief.
“A competitive federal program currently funds the DNR to help cities of under 5,000 citizens with tree inventories,” continues Tauke. “Funding for public tree removal and planting of replacement tree species is currently left to cities to figure out on their own. How Burlington meets the challenge in times of tight budgets will set the stage for how Iowans confront EAB infestation as it spreads across the state. The best we can do is to try to slow EAB movement.
“Another important issue is what to do with the dead infested trees. Estimates have ash trees at about 15 percent of our urban and rural forests. That’s a lot of wood in a relatively short time to make decisions about.”