Fort Wayne started losing what eventually would amount to at least 15,000 trees to the emerald ash borer a decade ago. But, the city’s excellent records of the pest’s damage could help save up to 1 billion ash trees in other cities across the county.
Records kept by the Fort Wayne Parks and Recreation Department helped a five-member team at Purdue University predict the progression of ash decline over time and conclude that saving the trees early is less costly than replacing them.
The team was led by Cliff Sadof, an entomology professor, and Matt Ginzel, an associate professor. It used Fort Wayne’s well-kept records because the Summit City was the first sizable community where trees were attacked by the pest after it arrived in Indiana in 2004.
The first U.S. sighting of the beetle was in 2002 in Ohio. It was found in Fort Wayne in 2006 “when we were just figuring out how to control these things and were experimenting with treatments,” Sadof said.
“At first we didn’t know how to protect the tree,” he said. “Then, we had to figure out how to do it and make it cost effective. We thought it was going to be a nightmare.”
Researchers in the Department of Entomology and Department of Forestry and Natural Resources at Purdue initially believed treatment would be required every year to save the ash trees. Protection methods included injecting soil near an ash tree, as well as some trunks, with Imidicloprid, an insecticide.
Experimenting with various approaches eventually reduced costs. Researchers found they could save ash trees by treating them aggressively three times during the first 10 years after damage from the beetle is discovered, Sadof said.
By then, the pest typically leaves a community because it has gone through the unprotected ash trees there. Three more spaced-out treatments will provide sufficient protection for the next 15 years, he said.
Fort Wayne lost 15,000 ash trees. Of those, 13,000 were street trees and 2,000 were park trees. Once the pest showed up in the city, the health of each ash tree was monitored every year until it was taken down if left untreated.
Records show whether a tree’s condition was excellent, with no canopy loss; good, with less than 10 percent canopy loss; fair, with up to 30 percent canopy loss; poor, with up to 80 percent canopy loss; or critical, with more than 80 percent canopy loss.
“The total cost for us to remove all the ash trees that were infested with emerald ash borer was $4.5 million,” said Natalie Eggeman, public information officer for the Fort Wayne Parks and Recreation Department.
“We’re trying to save 1,000 ash trees; it costs between $30,000 and $40,000 a year,” she said. “Along Clinton Street next to Headwaters Park there’s a whole line of ash trees lining the streets in the right-of-way. And also in Freimann Square we have some ash trees.”
Costs for treatment and for tree removal are substantially lower when done on a large scale. In Fort Wayne, the cost is about $30 per tree treatment and $300 per tree removal. For six tree treatments over 25 years, the cost would come to $180.
“We felt it was very important to try and save a percentage of the ash trees, so we evaluated all of the ash trees in our community and picked ones based on health, location, size, and benefit to the surrounding area,” Steve McDaniel, the department’s deputy director, said in an email.
“Of that, we found just over 1,000 ash trees that met that criteria. We started the treatment of those trees,” he said. “We treated 200 trees downtown and the remaining 800 were split up per quadrant, averaging 200 per quadrant.”
In 2011, the estimated retail value of about 12,000 ash trees remaining in the city’s right-of-way came to $28.8 million. The net annual green benefit from the remaining ash trees came to $1.8 million in energy savings and root system storm water cleaning.
A model developed by the Purdue team to predict the progression of ash canopy decline was funded by the U.S. Department of Agriculture’s National Institute of Food and Agriculture and Indiana’s Agriculture Science and Extension for Economic Development funding. It used data from Indianapolis and Lafayette as well as Fort Wayne.
The highly destructive beetle has killed tens of millions of ash trees across the Midwest. But, there are still 7 billion ash trees in the United States and up to a billion of them are in cities.
A number of cities, including Evansville, are working with Purdue’s researchers to do what they can to save as many of their ash trees as possible, Sadof said. Often a tree has lost too much of its structural integrity to save by the time it has lost 30 percent of its canopy.
The researchers developed a web-based cost calculator, which compares the cost of replacing or saving an ash tree, depending on the amount of damage the pest already has done to it.
Their findings have been accepted for publication by Aboriculture & Urban Forestry and will appear this fall in its article, “Tools for Staging and Managing Emerald Ash Borer in the Urban Forest.”
Since it was first spotted in the United States, the pest has spread to 25 states and two Canadian provinces, killing at least 500 million ash trees.