University Park, Pa. -- Elm yellows, a disease affecting Penn State's landmark American elm trees on the University Park campus and previously thought to have the ability to decimate the majestic trees, may be isolated.
The University's elms seem to be responding well to treatment and, according to Gordon Turow, director of campus planning and design, surviving elms appear to be safe for the winter. So far 37 trees along Schreyer Lane -- which leads to the University president's home, Schreyer House -- and 17 trees on campus have been or need to be cut down because of the effects of the disease. This total of 54 affected trees is a lower number than originally expected. Turow said they are still monitoring the situation, but it seems that the elms on Burrowes Road and Schreyer Lane are the only trees still at risk.
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. Elm yellows has devastated trees in 22 states.
The leafhopper arrived at University Park most likely via storm winds. It is also possible the disease can spread through root contact. Because contaminated trees will never recover and preventing spread of the disease is necessary, these trees have been removed over the winter.
"You cut down a historic elm tree, people notice," said Jeff Dice, supervisor of grounds maintenance. "We are sampling every tree to detect the disease and control the spread before removing it."
Dice said that to prevent a similar situation on campus in the future, the removed elms will be replaced by a diversity of species, so if a particular tree population is diseased, the impact won't be as significant. Ash, oak and hemlock trees throughout the country are also fighting their own afflictions.
Once a tree dies the organism dies too, Dice said. The wood from the trees is sold and the money goes toward planting more trees and funding alumni scholarships.
The University has created an interactive Web site at http://elmyellows.psu.edu to keep the Penn State community informed about ongoing efforts to understand issues relating to elm yellows and the campus elms, and to facilitate public discussion of these issues.