Forest & Grassland Health

Spruce Bud Blights

Camarosporium sp.
Dichomera gemmicola A. Funk & B. Sutton
Gemmamyces piceae (Borthw.) Casagr.

Host(s) in Alaska:

black spruce (Piceae mariana)
Colorado blue spruce (P. pungens); ornamental
Lutz spruce (P. glauca x sitchensis)
Sitka spruce (P. sitchensis)
white spruce (P. glauca)

Habitat(s): Buds, twigs

 

Dichomera gemmicola on Sitka spruce near Juneau.

Dichomera gemmicola on Sitka spruce.

 

Topics


Photos

Click on image for larger version.

Fruiting bodies of Gemmamyces piceae on white spruce near Anchorage, AK.

Fruiting bodies of Gemmamyces piceae on white spruce near Anchorage, AK.

Black, swollen, and misshapen buds with fruiting bodies of Gemmamyces piceae on white spruce near An

Black, swollen, and misshapen buds with fruiting bodies of Gemmamyces piceae on white spruce near Anchorage, AK.

Deranged growth caused by Gemmamyces piceae on white spruce near Anchorage, AK.

Deranged growth caused by Gemmamyces piceae on white spruce near Anchorage, AK.

Deranged growth of ornamental Colorado blue spruce caused by Gemmamyces piceae near Homer, AK

Deranged growth of ornamental Colorado blue spruce cased by Gemmamyces piceae near Homer, AK.

Dichomera gemmicola on Sitka spruce near Juneau with multiple affected buds and crooked shoot growth

Dichomera gemmicola on Sitka spruce near Juneau. This fungus looks very similar to Gemmamyces piceae.

Current Status & Distribution in Alaska (2020 Update)

We continued to document spruce bud blight throughout Southcentral and Interior Alaska. We found nine instances of Gemmamyces piceae south of the Alaska Range and one occurrence to the north near Delta Junction. Dichomera gemmicola was found in three locations south of Anchorage and a single Camarosporium occurrence was found along the Denali Highway. Five bud blight sightings are unidentified because they were not collected for microscopic verification of the causal fungus. No bud blight was detected in Southeast Alaska in 2019 or 2020, consistent with apparently lower disease incidence and severity. None of these fungi had previously been reported from Alaska prior to 2013, although D. gemmicola and Camarosporium have been known for decades in other parts of North America. Gemmamyces piceae is known as a tree killer in Colorado blue spruce plantations in Central Europe, but we have not seen mortality in Alaska. We have sequenced the total genome of this fungus and are using it to design a population genetic study to determine how long the fungus has been present in Alaska.

In 2017, we installed monitoring plots (182 plots) and conducted informal surveys to gather presence/absence information and disease severity information statewide. In conjunction with this intensive sampling effort, Dr. Gerard Adams (University of Nebraska Lincoln) determined that identical signs and symptoms were caused by three different fungal pathogens. Despite an effort to collect sexual fruiting structures of G. piceae in Alaska in 2017/2018 for a population genetics study, this fungal pathogen has proven extremely difficult to obtain in pure cultures. This work was intended to provide insight as to how long the fungus has been present in Alaska based on genetic diversity. Higher diversity would support a relatively longer time-since-establishment and likely native status. Its widespread occurrence, generally low levels of damage, and infections dating back a decade or more at many sites suggest it is native or long-established, while the lack of reports in Alaska prior to 2013 and limited detection in North America may point to a more recent introduction. 

Overall, blighted spruce buds have been documented at more than 200 locations in Alaska on white, Sitka, and Lutz spruce (Sitka-white spruce hybrid) in the forest, and Colorado blue spruce in ornamental settings (Detection Map). There has been no observed mortality from the disease; most affected trees have trace infection (1-5%), although some trees have up to 100% of buds infected. In 2018, there was a need to revisit some observation sites where disease was attributed to G. piceae without microscope verification or collection (before the presence of other causal fungi was known). We have confirmed Gemmamyces piceae at 31 sites from near Anchor Point to north of Fairbanks. Fairbanks appears to be a hotspot for this fungus but that may be an artifact of sampling effort. Gemmamyces piceae has not been found in Southeast Alaska. Dichomera gemmicola has the widest distribution. It has been found on white and Lutz spruce from near Lake Clark on the Alaska Peninsula, Talkeetna, and Chicken; it has not been found near Fairbanks. Dichomerra gemmicola is the most common bud blight on Sitka spruce in Southeast, but can be difficult to detect without dedicated surveys due to its very low damage severity and subtle symptoms. Camarosporium is more prevalent on white spruce in Southcentral up to the Alaska Range, with single points near Fairbanks and on a Sitka spruce in Southeast, respectively.

 

Return to top

Historic Activity

Blighted spruce buds (entirely or partially dead from a fungal infection) were first noted in Alaska on ornamental Colorado blue spruce near Homer in 2013. In 2014 it was found for the first time on native white spruce in the forest near Anchorage. Identification of Gemmamyces piceae by Forest Health Protection in Alaska became possible with a 2016 publication reporting a sudden spruce bud blight outbreak in Colorado blue spruce plantations in the Czech Republic (Cerny et al. 2016). The publication describes a massive outbreak that was first detected in 2009 and has now been found across the Czech Republic. Bud loss quickly reached 80-100% in highly infected trees and stands. The fungus has been reported since 1906 from Austria, Czech Republic, Denmark, Finland, Russia, Scotland, and Switzerland (Borthwick 1909). In these locations, it has primarily been found in human-altered situations (e.g., urban ornamentals, nurseries and forest plantations) on the North American tree hosts Colorado blue spruce and Engelmann spruce, but Sitka spruce and white spruce were also susceptible to a lesser degree. Neither the fungus, nor the disease it causes, were found within the native range of Norway spruce in Europe until 1946. It has been speculated that the fungus is native to Asian spruce from the Tianshan Mountains in China (Cerny et al. 2016). However, a recent paper made an apparently unsupported claim that it is widespread in North America (Jaklitsch & Voglmayr 2017). Only two prior North American records have been located, both from 1990 in New Brunswick and Nova Scotia on the east coast of Canada. Dichomera bud blight was first described in the early 1960s from British Columbia, where it has been more frequently reported on inland Douglas-fir, Engelmann spruce and white spruce than on coastal Sitka spruce (Funk and Sutton 1973). This disease usually is not a significant concern.  

Symptoms, Biology & Impacts

These diseases are recognized by black, swollen, misshapen buds and deranged growth patterns. The causal fungus infects through the bud and may kill buds prior to bud break. Infected shoots that are not killed characteristically grow around developing lesions, resulting in twisted, zigzagged branches and axillary bud proliferation. The symptomatic branch can be used to date the original infection (based on the affected branch cohort). After several years of bud loss, trees may wither and die.

Our observations to date suggest that Camarosporium sp. is a weak pathogen. The fruiting structures tend to be produced less densely, primarily towards bud tips. Affected stems seldom exhibit zigzag growth patterns.

Survey Method & Frequency

In 2017, 182 plots were installed to evaluate presence/absence of bud blight statewide. Three different sampling designs (fixed-radius plots, timed meanders and transects) were employed depending upon location, access, and available resources. FHP installed monitoring plots near Anchorage and Fairbanks in 2016 and found that damaged buds affected up to 40% of the trees within 50ft-radius plots. Most affected trees have very few damaged buds (less than 5%), but highly infected trees can have up to 100% of the buds dead or damaged.

Return to top

Collection Instructions

Spruce bud blight samples collected throughout the state will be used to improve our knowledge of bud blights in Alaska. Samples of Gemmamyces piceae may be suitable for a population genetics study. If you encounter black buds on spruce and would like to submit a sample to our Forest Health group for identification, please do the following:

  1. Take a clear, close-up photo of the affected buds. Many cameras can collect location information, which may be useful. Digital photos can be e-mailed. Photos alone will not allow for species identification.
  2. Collect a sample by clipping off the last few inches of the infected shoot.
  3. Put the sample in a paper bag (plastic bags create conditions for rapid sample contamination/deterioration). If possible, collect samples from three trees per site. Samples from individual trees should be stored in separate paper bags. Keep samples shaded and cool.
  4. Label the paper bag/s with the date, your name and contact information, the species of spruce (if known), approximate tree size (diameter in inches) and as much location information as possible (latitude/longitude is preferred, also names of nearby landscape features).
  5. If possible, estimate the percentage of buds affected on the collection tree (e.g., trace-5%, 6-15%, 16-35%. 36-67%, 68-100%) as a measure of disease severity. Include this information on the collection bag.
  6. Send samples promptly to: Robin Mulvey, Juneau Forestry Sciences Laboratory, 11175 Auke Lake Way, Juneau, AK 99801. Please send an e-mail (robin.mulvey@usda.gov) so that we know to expect a sample.

Detection Map

Click on the map image for a larger version.

Spruce bud blight locations in Alaska in 2020.

Detection locations of three bud blight fungi in Alaska as of 2020 showing the distribution of the spruce hosts (Picea spp.). The modeled spruce distribution was developed by the Forest Health Technology Enterprise Team in 2011 (240m-resolution, based on dominant tree species by tree diameter).

 

Links to Resources & Publications

1 Černý, K., Pešková, V., Soukup, F., Havrdová, L., Strnadová, V., Zahradník, D., & Hrabetová, M. 2016. Gemmamyces bud blight of Picea pungens: A sudden disease outbreak in central Europe. Plant Pathology, 65(8): 1267-1278. Available here.

2 Borthwick A.W. 1909. A new disease of Picea. Notes from the Royal Botanic Garden, Edinburgh, 4: 259–61.

3 Jaklitsch W.M. & Voglmayr H. 2017. Three former taxa of Cucurbitaria and considerations on Petrakia in the Melanommataceae. Sydowia 69: 81–95.

4 Funk, A. and B. C. Sutton. 1973. A disease of conifer buds in western Canada associated with Dichomera gemmicola n. sp. Canadian Journal of Botany 50(7): 1513-1518. Available here.

Forest Health Conditions in Alaska - 2016

Global Diversity Information Facility - Gemmamyces piceae

USDA National Fungus Collection Database - Gemmamyces piceae

Natural Resources Canada- Pacific Forestry Centre's Forest Pathology Herbarium DAVFP Collections Database - Dichomera gemmicola


Content prepared by: Lori Winton, PhD Southcentral and Interior Alaska Forest Pathologist, Forest Health Protection, loretta.winton@usda.gov and Robin Mulvey, Southeast Alaska Forest Pathologist, robin.mulvey@usda.gov.
 

Return to Damage Agent Info/Homepage
Return to top





https://www.fs.usda.gov/detailfull/r10/forest-grasslandhealth/?cid=FSEPRD535386&width=full