For me, this story begins in May of 2021 as I was delivering Mountain Home magazines, heading north from Avis to Blackwell. By then, the leaves were out on all the trees along the road, and I was looking forward to a drive in a green vista. Any bare, brown spots would be a stand of ash trees, killed by the emerald ash borer, or hemlocks infested with wooly adelgid. It was possible I would see trees damaged by gypsy moths. But the brown trees I was seeing were white pine. And there were many with brown needles. By the next trip in June, the pine trees looked no better. Even stranger to me were the blank looks that I got from friends when I mentioned what I was seeing in the forest. Was no one else seeing this? Turns out that I was talking about it to the wrong people.

For Bill Laubscher, forester in the Bureau of Forestry’s Northern Division, which includes the Tiadaghton and Tioga State Forests, this story began in 2016, with a phone call asking District 16 to look at some white pine that was yellowing the first week of June. The Department of Conservation and Natural Resources has been monitoring the progress of white pine needle disease since then. What I was looking at was not the beginning of the disease, but the end. These were trees that had white pine needle damage in the crown and were not going to survive.

“It was unexpected to see it [the mortality] so soon,” explains Jill Rose, forest pathologist for DCNR. What looks like one disease is a combination of several pathogens that attack white pine. In addition to white pine needle disease, affected pine stands are weakened by caliciopsis canker, a fungus that affects the trunk, white blister rust, and root rot. However, unlike what is killing the hemlock or ash, these diseases and pathogens are native and are normally found in the pine forest. But if they’re native and commonly found in stands of trees, why are the trees dying?

One of the factors that has changed recently is the climate. We have had a decade of wet springs.

“Odd patterns of moisture are hard on trees. Currently, there is a base level of stress for all trees,” Jill says, adding that the white pine decline is complex, but this change in recent weather is a large contributing factor. Although this cycle of disease has always been part of the white pine regeneration cycle—killing weaker, smaller trees and making room for stronger young trees—wet conditions, especially in the spring, have made these diseases much more widespread. Those conditions allow for a larger production of spores to be produced, and that’s when the damage happens. That damage we see in the trees now is the work of last year’s pathogens. The actual death doesn’t come from white pine needle disease, but from the caliciopsis canker and the root rot that can establish itself in a weakened tree.

“Caliciopsis canker is the nail in the coffin,” Jill notes.

According to Sarah Johnson, forest health specialist in the Northern Division, “Root rot is an insidious killer, and hard to detect until it’s too late. The first deaths are in poor soil locations.”

The disease is not widespread in all the Northern Division, but is concentrated in certain areas, one of those being the Pine Creek Valley. Bill explains why Pine Creek trees are prone to the diseases: “It’s a foggy microclimate.” In years when the spring is wet, the foggy valley is simply wetter, and the damp air is around the trees longer. That generates more spore activity and more disease. The dampness gives the disease the perfect conditions to get established in another host.

Most of the research on white pine needle disease comes from New England, where commercial pine lumbering has been affected by this death cycle. William Livingston, from the University of Maine, has done much of this research. The university has produced reports on the various pathogens that can contribute to the death of these trees, and an identification guide—Field Manual for Managing Eastern White Pine Health in New England—was published in June 2019, complete with photos of the various pathogens as they appear on the eastern white pine. There is a multi-state effort to both research and combat the disease.

The main approach to combat these diseases involves thinning the trees. This can be effective in a New England pine plantation, but Pennsylvania’s forests are different. The white pine in Penn’s Woods is not in a single species planted plantation but is part of a natural mixed forest. There are areas of heavy stands of white pine intermixed with hardwoods. These trees are not easy to reach. They are often on the sides of steep hills, not the flatter land of a woodlot where thinning is more possible. For foresters and DCNR, this is yet another change and challenge in the Pennsylvania forest that does not have a quick or easy solution.

For visitors to the forest for recreation and renewal, it is a sign of environmental strain and stress, as trees attempt to adapt to climate variation and change. Jill’s prediction from a recent seminar is that we can expect to see more deaths of mature trees this year as the cycle continues. That means more bare spots and brown needles on my trips through the Tioga and Tiadaghton State Forests. Again, wet and cool springs are ideal conditions for spread. Some of the literature about it makes it sound not too bad, but it has become a killer in our forests.