The fungus infects the bud of spruce trees, turning the normally gold-brown buds black, and folding them over. It’s not known if Gemmamyces piceae is a new forest pathogen, or an old one which Alaskan trees may already be resistant to. (Alaska Forest Health Protection)
A potentially harmful pathogen called spruce bud blight has now been identified in Sitka.
The fungus first appeared on the Kenai Peninsula in 2013, and has since been found in many locations around the state.
Researchers with the Forest Service are trying to determine how widespread spruce bud blight has become, and what kind of threat — if any at all — it represents for Southeast forests.
Update, August 31, 2017: Shortly after the Forest Service reported on the discovery of spruce bud blight (Gemmamyces piceae) in Sitka, a microscopic spore analysis determined that the fungus was actually a benign relative Dichomera gemmicola. Nevertheless, the discovery is scientifically significant. See a related story here.
Spruce bud blight is a known killer of trees. But it hasn’t killed any forests in North America yet. The Forest Service found the fungus in 2013 on the Kenai Peninsula. Three years later molecular geneticists sequenced the gene and compared it to known forest pathogens. The results were a wake-up call.
“The match was to specimens that were part of a paper published in 2016 from the Czech Republic.”
Robin Mulvey is a pathologist with the Forest Health Protection office in Juneau. She spoke recently at a lunchtime meeting of the Sitka Ranger District staff.
“And that was a pretty alarming match because that paper describes outbreaks of this disease on Colorado blue spruce in the Czech Republic leading to major plantation failure. So now we know that it’s a disease that’s potentially a tree killer, and we know that at least one North American spruce is highly susceptible to it.”
This map reflects the distribution of spruce bud blight in Alaska — prior to recent surveys in Southeast. Ketchikan remains the only place in the boreal and temperate forest zones where the fungus has not been found. (Alaska Forest Health Protection)
But there are two main things we don’t know about spruce bud blight, scientific name Gemmamyces piceae. The first: How widely distributed is it? The second: Has it been here all along, and simply no one ever identified it?
Answering the first question is a matter of logistics. The Forest Service has found the fungus from Kenai to Fairbanks. Now the agency is taking a close look at Southeast. Mulvey and her colleague, entomologist Liz Graham, have spent a lot of time on the road.
“So we’ve been sampling mostly in Juneau, but we also have monitoring plots on Zarembo Island, Wrangell Island, Mitkof, Kupreanof, Skagway, Haines, and now here in Sitka — and Ketchikan. That’s the work that we’re here doing this week. We’re installing these very simple plots — and not actually monumenting the plots in any way, except for collecting a gps point at the plot center. 50-foot radius plots and we’re assessing it for both spruce aphid and bud blight.”
So far, Mulvey has found spruce bud blight in every community she’s surveyed — with the exception of Ketchikan. Nevertheless, there’s really not much of it. In Sitka’s Starrigavan Valley, she found it in only two trees.
The second question — was Gemmamyces piceae here all along? — is more complicated. And it’s part of the reason the Forest Service is not going to war on spruce bud blight. The highest concentration of infection that Mulvey has ever seen was on a blue spruce in Juneau. A resident bought the tree from Home Depot as an ornamental for the yard. When it didn’t thrive, she threw it behind a shed, where it developed a major blight infection.
Mulvey found some blight in Sitka spruce trees near the shed, but she doesn’t know if the blue spruce was the carrier of the disease, or the victim of an infection that local trees are resistant to.
“One thing that I think a lot of people don’t know is that it can be really difficult to determine if something as small as a fungus is native or not. If it could have just been missed before. Maybe it’s always been here before and just not noticed.”
And spruce bud blight is difficult to spot on otherwise healthy trees. A normal bud is golden brown, and eventually will break out into a spruce tip — which many Sitkans harvest for flavoring syrup or beer.
Infected buds turn black and wither. Mulvey shows the group a specimen from Starrigavan.
“This main bud and shoot is dead — and it’s not only dead, it’s dead and curled over.”
Mulvey describes her office’s work right now as “information gathering.” Spruce bud blight is just one of many potentially harmful pathogens and invasives the Alaska Forest Health Protection office monitors. Mulvey says it may take an inoculation study across all North American species of spruce to determine the risks that blight poses.
In the meantime, once she and Graham finish their distribution study this summer, Mulvey says “We’ll be asking a lot more questions.”
