AMES, Iowa — Iowa State University removed about three dozen ash trees on campus last week in an effort to prepare for the arrival of the emerald ash borer, an invasive species from Asia that has caused the death of tens of millions of ash trees in 14 states since its detection in the United States in 2002.
Although some experts expect its arrival in Iowa in significant numbers to be five to 10 years away, evidence of the emerald ash borer was found last spring in a tree on an island in the Mississippi River in Allamakee County.
At ISU, the Facilities Planning and Management department has been planning strategies for the insect’s arrival for several years, dating back to 2005.
Les Lawson, manager of facilities maintenance at ISU, and Rhonda Martin, landscape architect for Facilities Planning and Management, said they have been tracking information about the emergence of the emerald ash borer from experts in Michigan, where the pest was first discovered in the United States.
“At the time, we didn’t know how encompassing this little insect was going to be,” Martin said. “But the experts in Michigan were telling us this is serious.”
Lawson said the university stopped planting new ash trees in 2005.
In 2007, facilities planning took an inventory of every ash tree on campus. Every one of the 1,260 ash trees on campus was cataloged and rated on a scale of one to five.
“We wanted to find out what we had in every tree,” Martin said. “Is this ash tree in great health? OK health? Is it in decline? We were in a fact-gathering mode.”
Facilities officials also worked with faculty to identify trees that were unique species or used for education purposes. Those trees were specifically earmarked for protection.
About 30 of the weakest ash trees, many of them dying, were removed over the past two years. Still, about 20 percent of the ISU campus tree population consists of ash trees. ISU’s goal is to gradually reduce their proportion to about 8 percent.
Lower densities of ash tree populations make them less attractive to emerald ash borer, ISU Extension Entomologist Mark Shour said.
“If you have a large concentration or group of any (tree) species, that sounds an alarm for when insect or disease problems do arise,” Shour said. “Landscape management like what is occurring on campus becomes an important factor.”
Last week’s removal of trees brings the density in the core area of campus down to 8 percent. Martin said other areas of campus will be addressed in future years.
Lawson said the public should not notice any significant reduction in the number of campus shade trees, and the number of trees removed falls within the normal range for an average year.
“If you consider we removed over 60 trees or parts of trees last summer just because of windstorm damage, this is not that significant,” he said. “We also replace trees on a one-to-one, or often more than one-to-one, basis.
“The whole idea with this plan is to phase out ash trees gradually over a period of years, so it isn’t as noticeable.”
The trees will be replaced with a large variety of shade tree species, including black gum, oak, Kentucky coffee, sugar maple and tulip trees.
Lumber from the removed the trees will become part of ISU’s “treecycle” program, which uses the wood for furniture, woodworking projects and mulch.
Martin said although the potential damage that ash borers can cause is troubling, the state of Iowa and the university have the luxury of time.
“Officials and experts in Michigan were telling us, ‘If only we’d had time to prepare,’” Martin said. “We have that, and we’ve been using that early warning and the time we have to have a strategy in place.
“We hope it makes all the difference.”