Because signs ask pedestrians to avoid the trees after they have been sprayed, the pesticide usage has some concerned about potential health risks.

"We might be better off without the elms because of the pesticides used on them," said Garrett Fitzgerald, Eco-Action public relations director. "But they do have a significant value to the community and campus."

About 300 of University Park's 11,000 trees are elms, and Penn State tree crews spend more than 40 percent of their time preserving them, said Paul Ruskin, Office of Physical Plant spokesperson.

"They can be looked at as an historical legacy that we are trying to keep in as pristine condition as possible," he said.

But the borough is unable to take such a proactive role with elms off campus because of the high cost of maintenance, Sam said. The borough also is restricted because it cannot stringently control elms on personal property.

"We're not planting American elms any longer because we're not confident we can control the disease," he added.

The elm bark beetle spreads the disease by carrying spores on their legs, Sam said. Dutch elm disease also moves through trees' roots. If an infected root brushes the roots of a neighboring tree, that tree can become infected. Elms lining entire streets can die that way, Sam said.

Another potential threat to trees in general is the Asian long-horned beetle, which affects maple, oak and poplar trees similar to the way the elm bark beetle affects elms. Thus far, Asian long-horned beetle outbreaks have been restricted to New York and Chicago, Sam said.

To control the spread of the beetles, towns may opt to cut down the infected trees as well as surrounding uninfected trees, Sam said. Such preventive actions taken in New York should stop the spread of the beetle to State College, but he is still concerned.