Four years into a 10-year project, Iowa State's proactive plan to prepare for the invasive emerald ash borer has reduced the campus ash tree density by about 25 percent. A diverse variety of tree species has been planted as replacements.
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"The insect is attracted to high-density clusters of ash trees," said Rhonda Martin, landscape architect in facilities planning and management. "Our original target was to reduce the ash tree population from 20 percent of the tree canopy to a more manageable 8 percent, and we have achieved that goal on central campus. Now we are working out toward the edges of campus with phased ash tree removals and replacements."
Iowa's Department of Agriculture issued a statewide quarantine on Tuesday to restrict the transfer of ash wood materials, such as firewood, after evidence of the emerald ash borer was discovered in Waterloo. Six Iowa counties have confirmed infestations: Allamakee, Black Hawk, Cedar, Des Moines, Jefferson and Union.
Long-term planning
Treecycling
Lumber from the ash tree project has seen new life on and off campus, thanks to FPM's TreeCYcle program. The alumni association plans to offer a limited supply of mantle clocks and keepsake boxes crafted from campus ash lumber in its online store later this year.
Iowa State began preparations for the inevitable arrival of the devastating insect more than seven years ago, with the help of state and ISU Extension and Outreach entomologists who developed the state's readiness plan (PDF).
Initially, FPM staff cataloged and rated the campus ash tree population (about 1,260). The weakest and most susceptible trees were removed first. Since then, 50 to 90 ash trees have been removed each winter. Martin said the residence, athletics and recreation services departments have joined the effort by providing additional funding for work beyond the central campus areas.
In four years, crews have removed 296 ash trees and replanted 299 replacement trees. Persistent drought conditions have slowed the replacement of the tree population, Martin said, but another 90 trees are scheduled to be planted this spring.
"Now that the emerald ash borer has been found in six Iowa counties, we are beginning to discuss what happens to the remaining 500 ash trees on campus when the pest is discovered in the Ames area," Martin said. "In the long run, what is the right number of campus ash trees to treat and protect? We don't have the answer yet, but considering recent news about another EAB discovery in Waterloo, we will need to decide soon."
