Vermont’s brown pines are not dead. They’re just a little sick.

A cluster of treetops
A tree gets rid of white pine needle disease by shedding all fungus-infected needles. Before the needles fall, they turn yellow and brown. Photo by Emma Malinak/VTDigger

As you drive through Vermont, you may notice that eastern white pine trees have turned yellow and brown and shed new needle growth.

But the trees aren’t dying, says Savannah Ferreira, the forest health specialist for the Vermont Department of Forests, Parks and Recreation. They are sick with white pine needle disease, which causes trees to lose needles infected with fungi.

“Otherwise, healthy trees will probably recover from this. So while it looks really alarming right now, once these needles drop, hopefully we will get green needles again, and it will look better for the rest of the growing season,” Ferreira said.

According to Ferreira, white pine needle disease is caused by fungal pathogens that thrive in wet, humid conditions. Just as mold grows in the dampest corners of a home, the fungi that cause the disease can spread quickly if the crowns of pine trees retain moisture over time.

With historic rainfall in Vermont last spring and summer, Ferreira said, fungal spores had an ideal environment to reproduce and attach to emerging pine needles. Those needles, which have grown with the disease throughout the year, now show the yellow and brown hues by which the disease is recognized.

And the locals are starting to take notice. Mike Clifford, a Killington resident, said he was concerned about the brown trees covering the hills along Routes 107 and 4 — largely because he’s never seen anything like it before.

“It’s quite noticeable. You see all these green trees, and then suddenly a big group of brown ones,” Clifford said. “It just seemed strange. … There seems to be an awful lot of these diseased trees.”

Ferreira said that while most of the reports she has received are from southern Vermont, the disease is not only prevalent statewide, but also in the Northeast. She said her team will conduct aerial surveys in late June or early July to gauge the extent of the problem, but there is currently no estimate of the extent of the damage.

In the meantime, Ferreira said locals can help limit the spread of the disease by not moving plant material, such as firewood, into new areas. There’s no need to cut down trees that look diseased, she said, because otherwise healthy trees should make a full recovery once they shed their infected needles. The fungi that cause the disease are not considered harmful to animals or humans, Ferreira said.

The real concern, she said, is whether the widespread damage now seen will become an annual pattern.

“If we get consecutive years of severe symptoms, it can cause stress (on trees) and over time that can certainly worsen other symptoms and lead to mortality,” Ferriera said.

Map of Vermont showing white pine needle damage in 2023, affecting 3,349 hectares of forest.  The map indicates areas of observed needle damage with dots marked in different regions of the state.
A map showing areas where White Pine Needle Disease damage has been observed. Map courtesy of the Ministry of Forests, Parks and Recreation

Eastern white pines grow in forests throughout Canada and the northeastern and mid-Atlantic United States, but New England’s changing climate – particularly increased spring temperatures and precipitation levels – has created conditions most conducive to its spread of the disease, according to a 2019 report from the University of Massachusetts Amherst. Repeated cycles of infection can “severely weaken trees” and lead to their death, according to the report.

Other than thinning white pine forests to slow the rate of infection and providing nitrogen fertilizer to help infected trees recover, the study found little can be done to stop the disease due to the “natural abundance and large size” of pines.

Department of Forests, Parks and Recreation officials have been monitoring the disease since 2010, when “sudden widespread white pine needle damage occurred,” according to the department’s annual report on forest, insect and disease conditions.

Since then, white pine needle disease has caused varying levels of damage from year to year – all depending on the previous spring’s weather conditions, which determine whether fungi will attach to new needle growth.

According to the 2023 report, the disease caused 3,349 hectares of observable damage last year, largely concentrated in Windsor and Orange counties. Ferreira said she expects the damage to be even worse this year.

According to the department’s annual report, damage was “widespread and severe” in more than 30,000 hectares of pine trees in 2016.

For now, Ferreira says all she can do is wait for the trees to grow new, healthy needles and cross her fingers that the disease won’t hit Vermont as hard next year.

“It certainly hasn’t been as wet as last year,” she said. “So I remain hopeful that our trees might be able to recover a little better next year.”

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