Last November, elm yellows disease infected 47 of the 400 elm trees on campus, prompting fears the campus's historic foliage could be at risk.
There's good news for tree lovers: This year, only three were afflicted.
"This is a moderate success, but we are not out of the woods, so to speak," Office of the Physical Plant (OPP) spokesman Paul Ruskin said.
A relatively new disease to Penn State elm trees, elm yellows has no known cure, said Kelleann Foster, chairwoman of the University Tree Commission.
"Every other place that it hit, it has wiped them all out," Foster said.
While elm yellows is isolated to two specific parts of campus -- Mitchell Road and Burrowes Road -- the disease is very present in other parts of the valley.
"When you leave the campus area, Penn State is in the midst of a raging epidemic," Ruskin said. "But we have teams of trained people dedicated to saving the elms and some of the best scientific guidance for plant pathology in the nation."
OPP Superintendent of Grounds Jeffrey Dice and plant pathology professor Gary Moorman led the team of OPP landscapers who collected this year's elm data.
Several factors contributed to the disease's decline, including a cold spring, Ruskin said.
"We think the cold weather has affected the leaf hoppers and decreased the number of nymphs on trees," he said, speaking about the disease's insect carriers and their young.
Elm yellows is spread by insects, although researchers have yet to isolate a specific carrier, Moorman said.
Another factor may be the antibiotic injections administered to some of the elms -- but Moorman said there is no evidence of that tactic's success, as targeted trees and those left untreated saw a similar decrease in the pathogen.
"The good news is that the infection rate has been suppressed, though we don't know what specifically is causing it," Ruskin said.
One infected tree was near Deike Building on Burrowes Road. The other two were located near Penn State President Graham Spanier's house on Mitchell Lane. Last year, most of the elms removed were in this area, part of the more than 50 removed to date.
These trees were replaced by different species, such as oaks, sycamores and tulip poplar trees, Moorman said.
Having one tree removed costs about $2,000. But Ruskin feels associated costs are well worth it. Many prospective students make their ultimate decision to come to Penn State based on its beauty and landscaping, he said.
"Elms are a part of the Penn State heritage, and it is hard to put a cost on something that is priceless," he said.
But the major problems for elms remain, including Dutch elm disease. The disease has been a problem for decades, although elm yellows only appeared on campus in 2007, Ruskin said.
"When trees have elm yellows, they become more attractive to bark beetles that carry Dutch elm," Moorman said. The tree removed on Burrowes Road had both diseases, he said.
Despite these threats to elms, Moorman said the weather might prove to be the most devastating.
"It is more likely we will lose more elms to snow storms, like the one we had a few weeks ago," he said. "They result in major damage to these large trees."
