A foliage disease has discolored the needles of pine trees between 7 Mile and 15 Mile Haines Highway, and an aerial survey by federal forest scientists later this month may help determine the extent and severity of the outbreak, and whether it merits more local study.
The disease, dothistroma septosporum or “red band needle blight,” is caused by a naturally occurring fungus that travels between trees on spores. According to the federal Forest Health Condition Report for Alaska in 2014, the disease doesn’t kill or significantly stress trees “under normal circumstances.”
But according to the report, more than three consecutive years of the disease have killed large portions of pine stands around Gustavus and Glacier Bay National Park.
“A localized outbreak of this disease in stand of shore pine-spruce-cottonwood and pure shore pine near Gustavus and Glacier Bay National Park has been ongoing since 2010 and is not subsiding,” the report said. Shore pine, or pinus contorta contorta, is a subspecies of lodgepole pine found in Haines and around Southeast.
A prospectus for a study of shore pine in 2011 by Forest Service pathologist Robin Mulvey said that between 2004-2008, shore pine suffered “statistically significant” losses in study plots in Southeast and Southcentral Alaska.
The prospectus said there were “several unusual aspects” to mortality of the trees, including that losses were significantly higher in larger trees and that there was no apparent geographic pattern to mortality.
In a brief interview this week from a remote field location, Mulvey said trees can typically survive an attack of the disease for a season, but can die if the attack continues for years.
A study of the same disease in lodgepole plantations in British Columbia suggests that it becomes epidemic when temperatures and precipitation climb at certain times of year, Mulvey said.
Forester Greg Palmieri this week said his office only noticed the roadside outbreak this year. He said the mountainside section of pines along the highway is likely the largest single stand of the trees in the valley.
Haines marks the northern boundary of the species, which might make it more susceptible to slight changes in climate or other conditions, Palmieri said. “A slight change in conditions can present itself in a dramatic fashion for a species living on the edge of its climactic zone,” he said.
Palmieri said his office has received several calls about the needle disease. “It just looks like the trees are dying, and they’re concerned.”
Palmieri said he’s also seeing more signs of spruce beetle attacks and potential spruce tree mortality in the local forest, possibly due to low snow loads in recent winters and warm, dry spring weather.
In her 2011 study prospectus, Mulvey said “there is virtually no baseline information on the insect and disease problems of shore pine…Due to its low commercial value, shore pine is understudied in Southeast Alaska and throughout its range.”
Unlike other parts of Southeast that have only shore pines, lodgepole and shore pines grow in the Haines area. It was unclear this week if the disease has also reached outbreak levels in lodgepole pines here.