By Joseph Robertia
As summer gives way to fall, seeing the trees change color is a common seasonal occurrence across the Kenai Peninsula. But, typically, it isn’t the evergreens that are transforming from green to orange, yet that is what is happening in many areas on the peninsula. Spruce tree needles are staring to rust at their tips, due to a form of fungus that utilizes black, white and Sitka spruce needles for a portion of its life cycle.
“The scientific name is Chrysomyxa ledicola. It has two stages, one on spruce and one on Labrador tea. So, typically, it affects spruce only in wetter areas where you have Lab tea as an understory plant,” said Todd Eskelin, of the Kenai National Wildlife Refuge, where the rust has been observed in several locations.
Labrador tea is a small, ground-dwelling, evergreen shrub with fragrant, white flowers. It has small, leathery leaves that are shiny-green on the topside, and reddish-brown with hairs on the underside. The flowers grow in clusters, and the plant height is typically between 1 and 3 feet tall.
The refuge isn’t the only place it grows, however, nor the only spot where the rust has been showing up on spruce. According to Janice Chumley, integrated pest management technician at the University of Alaska Fairbanks Cooperative Extension Service, in Soldotna, many questions have come in from peninsula residents wondering about the growing orange color at the tips of spruce trees around their homes and neighborhoods.
“I’ve had a lot of calls from people curious about what it is. It’s dominant in some areas, absent in others. Areas in Clam Gulch and Homer have been well-coated, but there are good amounts reported in Ninilchik and Nikiski, as well,” she said.
Even in these regions, Chumley reaffirmed what Eskelin pointed out, that the wetter the area is, the more fungus that seems
to be present.
“Bogs and swampy, wet areas — anywhere where there’s a lot of water — there seems to be more rust than on spruce from upland, drier areas,” she said.
Michael Fastabend, a program coordinator for the Kenai Peninsula Borough Spruce Bark Beetle Mitigation Program, said that, in addition to the wet/dry factor, there is another reason the rust may be prevalent in one stand of spruce and nonexistent in another stand nearby.
“The spores have about a 1,000-foot range, about a fifth of a mile, so that’s why you see such a dramatic demarcation. The spores may be at the end of their 1,000-foot range,” he said.
As to the reason the rust is showing up now, Fastabend said there are two answers, the first of which is related to the mild start of the warm-weather season.
“Historically, the rust is more prevalent in cool, wet springs, like we had this year,” he said. “But it does tend to show up about every three to four years.”
So if spring was damp, why is the rust only showing up now? Fastabend explained that it has been present all season and is only becoming apparent on the spruce because it is in the second stage of its life cycle.
“It overwinters on the Labrador tea and releases spores in spring that attack the spruce needles that are the new growth of this year. These have the most nutrients for the fungus to grow, so the spruce needles succumb in summer,” he said. “And what we’re seeing now will spore out to land on the Lab tea and repeat the cycle again.”
While the rust may be unattractive to some, it is nothing for homeowners to be concerned about if present on trees on their land. The spores can cause a premature defoliation that may influence tree growth but, otherwise, little damage typically occurs unless the tree is infected for several consecutive years.
“Some homeowners will try to remove the infected branches, but there’s no real reason to,” Fastabend said. “It’s really just a cosmetic thing. It doesn’t really hurt the tree.”