What’s killing red pines?

Scientists study mysterious die-off in Stephenson Range near Wilmington

By Mike Lynch

Scientists are trying to find out what killed many of the red pines on the eastern edge of the Stephenson Range near Wilmington. Dozens of trees, perhaps hundreds, have died in recent years. They are located above 2,000 feet, within a few miles of the hiking trail leading to Cooper Kiln Pond. Most of the trees are still standing.

The Adirondack Explorer visited the site in late September with Zack Simek, terrestrial plant coordinator with the Adirondack Park Invasive Plant Program. He said the trees may have been killed by an invasive pest, but he saw no evidence of that during the visit. “There’s probably more than one thing at play that’s causing the die-off,” Simek said. “It may have started as poor site conditions from something like drought and shallow soils. There were probably some native insects that moved in and began to feed on the trees. But what exactly is causing them to die is still unknown.” If a combination of factors killed the pines, the die-off might be an isolated case. But if an invasive pest or another environmental factor, perhaps associated with climate change, is to blame, the die-off could be a harbinger of a regional problem.

The only other die-offs of red pines that Simek has heard about occurred on Lake George islands. He didn’t know the cause of those die-offs there either. However, they were small in comparison. In fact, the die-off in the Stephenson Range, where a half-acre might be affected, is the largest he’s seen in the Park—of any tree species. The die-off has been occurring for several years but seems to have become more widespread recently. The state Department of Environmental Conservation is among the organizations evaluating the situation. DEC forester Rob Daley visited the site in September, as did Seth Jones of the Adirondack Mountain Club and Brendan Wiltse of the Ausable River Association. The association posted a photo of dead trees on Facebook shortly afterward.

“We found several stands of red pines where all, or most, of the trees were dead or dying. No other species appeared to be affected,” the Facebook post said. “There are several invasive insects that target red pine, including sirex woodwasps and red pine scale. When we learn more about what is affecting this stand we will share it with you.” Red pine die-offs have occurred in other northeastern forests for years and are the subject of scientific studies. Barbara Schultz, manager of Vermont’s forest health program, said die-offs have been occurring in her state for at least a decade. Aerial studies this year detected 39 locations in Vermont, totaling 516 acres, where red pine stands were in poor health or dead. Schultz noted that many of the stands were red pine plantations. “It’s a little premature to be confident of the cause because the research is ongoing, but one of the things that was detected in Vermont as a consequence of the research is red-pine scale,” she said.

The scale is an insect (an adelgid) from Asia that has killed red pines in southern New England and parts of New York. “It’s something we didn’t know we had in Vermont before,” Schultz said. Red-pine scale has existed in the southern region of New York state for decades, but scientists interviewed by the Explorer know of no evidence that it is in the Adirondack Park.

Top photo: Zack Simek speculates that a combination of causes may be killing the trees. Photo by Mike Lynch