Ash trees on campus are being removed because of an invading species referred to as the emerald ash borer.

There are around 1,200 ash trees on campus, and 36 ash trees have been cut down.

“The emerald ash borer is a tiny, green beetle that has devastated ash trees in urban and forest settings,” said Rhonda Martin, landscape architect for facilities planning and management.

Like many other invading species, the emerald ash borer came into the U.S. unnoticed and slowly spread into other states.

“The emerald ash borer came in and started at Michigan, and by the time they realized what they were, they had a large infestation of these insects in Michigan,” said Lester Lawson, manager of facilities maintenance. “It has since progressed through Michigan, Wisconsin, Minnesota and at this point is on the eastern border of Iowa along the Mississippi River.”

According to experts, the emerald ash borer is expected to arrive in Ames in about 10 years, although it could be sooner.

It could possibly be next year if a log that is transported to Ames is infested with the species, Lawson said.

The emerald ash borer feeds only on ash trees.

“Like most insects, it’s plant specific,” said Donald Lewis, professor of entomology. “It feeds exclusively in branches and trunks of ash trees.”

The plan is to keep the spread of the emerald ash borer to a minimum.

“The worst thing is as the trees die people cut the wood up, and then they transport the wood to new areas, and when they do that they distribute the insect,” Lawson said. “If there are ash trees in that area where it’s being transported to, then you have an infestation in that area.”

Lewis said, “We need to make sure to not remove any firewood outside unhealthy areas and begin replacing firewood while we have the chance.”

The only solution to deal with the invasive species is by removing all of the infested ash trees.

“You could do nothing and let it get here, and all of a sudden you’ve got 1,200 trees to remove,” Lawson said. “Or you can plan ahead and take a few trees and start replacing them so you don’t have 1,200 trees at once to take out.” That’s what they have chosen to do.

The ash trees will be replaced with other types of trees after they are removed.

“We’re decreasing the density of ash trees we have in our urban forest in a small manner phase through 10 years,” Martin said. “At the same time we are increasing the diversity of our overall tree species. For every ash tree that comes down, a different tree will be planted.”

The ash trees on campus make up about 20 percent of the overall tree canopy.

“A healthy environment on campus would be about eight percent ash trees on campus,” Lawson said. “We are going to try to get our ash population down to an eight percent level on a gradual basis and replace tree for tree as time goes on here.”

The ISU Facilities and Planning Management staff has received support for their plan.

“We received funding of $30,000, which will pay for the tree removal and the tree replacement,” Martin said.

The staff is also working with the Outdoor Teaching Committee, which is made up of faculty members from landscape architecture, forestry and botany.

“The committee was part of the people that we went to ask them about our program and recommendation for what trees not to remove,” Martin said. “We are trying to pick out the trees that are stressed, weakened or positioned in an area where they are harder to preserve.”

Martin hopes that with the time they have now they will be able to adjust for the arrival of the emerald ash borer in the next 10 years.

“We are trying to thin the population and provide something that is more diverse and less attractive for the arrival,” Martin said.