University Park, Pa. -- Penn State continues to battle the two primary diseases threatening the landmark American elm trees on its University Park campus, but crews also have begun planting new varieties of trees to replace those elms lost during the past several years on the Allen Street Mall area.
Workers began this week planting more than two dozen trees on the campus' historic core. The plantings include an array of shade trees that grow in Pennsylvania, including coffee trees, plane trees, bur oaks, white oaks and zelkovas. Different types of trees are being planted to guard against a future large-scale loss to disease.
"It's difficult for us to predict what the next introduced problem will be," said Jeff Dice, supervisor of grounds maintenance in Penn State's Office of Physical Plant (OPP). "Because of the world we live in -- the way we move and our global economy -- the potential for introduced species that damage our trees becomes a problem. This is really a 100-year decision. By diversifying the tree selection, we're hoping to make it a little more resilient to future attacks and we hope the trees will make the same visual statement for the next 100 years as the elm canopy did."
Introduced, or non-native, species such as the the European elm bark beetle, Asian longhorned beetle and gypsy moth can spread foreign diseases for which native plant life has no defense.
The two diseases facing one of the nation's oldest elm stands are Dutch elm disease, a fungal disease spread by the elm bark beetle, and a more recent syndrome known as elm yellows. Dutch elm disease has devastated native populations of elms for decades, and native trees have not had the opportunity to evolve resistance to it. Elm yellows, a bacteria-like organism spread by a tiny insect called the whitebanded elm leafhopper, infects the tree's root cells and the inner bark that carries nutrients to all parts of the tree. An infected tree cannot receive adequate nourishment and, by the end of summer, the tree's leaves turn yellow and the tree dies.
Currently, the elms are at "the highest risk level," Dice said. Elm yellows has slowed on campus but is devastating trees in the surrounding region. Trees that had been infected, meanwhile, provided ideal conditions for elm bark beetles to spread Dutch elm disease.
Though Penn State has had a concerted effort in place for more than 50 years to fight Dutch elm disease, elm yellows only began to appear in campus trees in 2007. Since then, 65 of the campus' approximately 290 elm trees have been lost to elm yellows and another eight have been taken by Dutch elm disease.
Forty-seven of the elm yellows losses came in 2008, but recent losses have been more moderate, with 10 lost in 2010. Though elm yellows has devastated trees in dozens of states and in the region surrounding the University Park campus, Penn State has been able to beat the odds, thanks to aggressive efforts and collaboration among several University units. Early data suggested all elms on campus could have been lost by now, which would have resulted in millions of dollars in replacement costs.
"The success with the elms has been because of the team effort across the University that has been put into it," Dice said. "It's a collaborative effort, and when you look at where we are compared to what was predicted, we've done a lot better than we had hoped. If you take any of those collaborative elements away, we won't have any more elms. Most municipalities that I am aware of or that have been cited in literature on this lost all their elms to elm yellows in a very short period of time. We're trying to manage it so that we do not lose a significant amount in any one year."
Although OPP is tasked with managing the trees, Dice said the elms could not have been preserved thus far without researchers in entomology and plant pathology who have provided data and explored new ways to detect elm yellows and combat infections. Penn State's Joel N. Myers Weather Center, meanwhile, has been vital in providing meteorological data that predicts when treatments can and should be applied. OPP also coordinates with State College borough officials.
The Office of University Development and alumni also have provided assistance. The members of the Class of 1996 established as their Senior Class Gift an endowment to support maintenance and replacement of campus elm trees. Since elm yellows was introduced, development officers have worked with OPP and the 1996 Senior Class Gift committee members to refocus the endowment to protect diseased elms and replace lost elms with a variety of different trees. The current planting of new trees is funded mostly through income from that endowment.
"I think that class is going to be proud to know their foresight put them in the right place to help," Dice said.
The Penn State Alumni Association also has helped ensure that the lost elms provide a benefit, working with OPP to create the Penn State Elms Collection, a line of high quality furniture and frames crafted from the downed elms. A significant portion of the proceeds from the sale of the furniture and frames goes to the class gift endowment and will support the planting of new trees in the future. Dice said sales have reached about $160,000. He hopes the combined efforts ultimately will provide funding support for campus trees in perpetuity.
Dice said Tom Svec, a local master craftsman for the Elms Collection, summed up best the importance of the program: "We owe it to the future to make the most imaginative use of what misfortune has provided us."
Alumni have responded enthusiastically to the collection, Dice said, because the elms have been so much a part of the University Park campus.
"Allen Street Mall was so magnificent in its time and people still talk about it," Dice said. "The key for us now is to manage the trees safely and replant strategically so we can continue to have a collection of high quality trees in this historic space."