Although the University of Nebraska-Lincoln has many trees in jeopardy if and when Emerald Ash Borer strikes its campuses, its landscape professionals already have taken steps to minimize the pest’s potential harm.
Ash trees account for a little more than one in 20 of the approximately 6,300 trees on UNL’s campuses. A recent count showed 378 ash trees, roughly split between the East and City campuses, said Jeff Culbertson, an assistant director for landscape operations.
The beetle, native to Asia, was confirmed for the first time in Nebraska last week in Pulaski Park in Omaha
Culbertson said UNL landscape personnel have been preparing for an invasion by Emerald Ash Borer for at least the past five years.
Some of the steps they’ve taken include:
Removing weakened and ailing ash trees. The borers are said to be attracted to sick trees first, then spreading to healthy ones, Culbertson said.
Nurturing healthy trees, keeping them mulched, pruned and well watered.
Choosing a variety of other tree species for new and replacement plantings.
Staying up-to-date on training and the latest information on the borers. Landscaping staff have been trained to recognize the symptoms of Emerald Ash Borer and they are certified to inject restricted-use pesticides into tree trunks to combat the pest.
“We haven’t planted ash trees for years, because we knew this was on the horizon,” said Eileen Bergt, also an assistant director in landscape services. “We’ve been planting a lot of other trees to provide diversity to the campus tree population.”
Culbertson said between 150 and 200 trees are planted on the UNL campus each year, for a variety of reasons. Some are to replace trees that have died, others are part of a new or renovated landscape.
Bergt said ash trees now are more likely to be cut down if they appear weak or if they are in a bad location.
Some of UNL’s ash trees are grouped in prominent areas, such as the loop on the east side of Memorial Stadium; near Hardin Hall and along Holdrege Street near East Campus; and along R Street and 16th Street on City Campus.
Yet Culbertson and Bergt said they doubt the borer will leave major empty spots on either campus.
“Losing all the ash trees is not something I’m planning on,” Culbertson said. “We’re going to maintain as many as we can. Because of other states’ experience with Emerald Ash Borer, the rest of us are better prepared and informed.”
Although an infestation of Emerald Ash Borers usually is fatal to American ash species, area experts reassure tree lovers that an infestation won’t kill the trees overnight.
“It will definitely have an impact on both campuses when it reaches Lincoln, but it could still be a couple of years before it arrives,” said Justin Evertson, green infrastructure coordinator with the Nebraska Forest Service. “Once it does get here, it will take maybe three to four years to move across campus.”
Preventive treatment is recommended to protect ash trees if the Emerald Ash Borer has been confirmed within 15 miles. Culbertson said landscape staff would try to save at least some trees by treating them with trunk-injected pesticides. UNL would probably not use pesticides that require drenching the soil around the base of the tree because of the greater potential environmental consequences. If the pesticide gets taken up by nearby plants, for example, it could harm bees and other pollinating insects.
While Evertson warned that pesticide treatment harms trees and is not a long-term solution, Culbertson said it now appears that the Emerald Ash Borer threat dissipates over time.
“We’re starting to identify the important trees on campus and making sure we’re protecting these first,” Culbertson said. “It appears if you can protect your area, after eight years the potential problem starts decreasing.”
The cost to treat a tree is about $100 every two years. Culbertson said his staff all are certified to apply the pesticides.
“We have a very diverse campus forest,” he said. “The number of ash trees is significant, but it’s a small component of our forest. That’s why we would work to save some of the ash trees. We’re a botanical garden and we want to maintain as many ash as we can for research.”