Notes on Mountain Alders and an Infectious Tongue Gall

Many of the Mountain Alders (Alnus incana subsp tenuifolia) in the Mazama area appear to be infected with the fungal disease Alder Tongue Gall (Taphrina alni).

Mountain alders are a dominant, deciduous tree species in riparian zones in Washington and Oregon that often forms thickets (Filip). It is a small to medium sized tree, usually growing to around 50 to 65 feet with a maximum lifespan of 60 to 100 years. A. incana has smooth gray bark, matt green ovoid leaves, and catkins reaching 5 -10 cm in length (male) or 1.5 cm long (female). Its tiny seeds are borne in egg-shaped cones, 2-3 cm long and 1-2 cm in diameter (Flora of North America).  

A healthy A. incana in bloom.
.Joe F. Duft. USDA NRCS. 1992. Western wetland flora:
Field office guide to plant species. West Region, Sacramento. 

            

Mountain alders are important trees in their riparian ecosystems. During the summer, A. incana provides critical shade to wildlife and the rivers they grow near, keeping the water at a cooler temperature vital for fish (Fillip). In addition, alders are pioneer species, meaning they are one of the first plants to colonize a disrupted or damaged ecosystem. To do so, alders have adaptations that allow them to grow even when conditions are not ideal. One such adaptation is their symbiosis with nitrogen-fixing bacteria that absorb nitrogen from the air and make it available for use by the trees (Tree Species Compendium). The alders' early presence in an ecosystem increases the amount of available nitrogen in the soil, making it possible for more vegetative species to follow (Featherstone).

A. incana in their riparian habitat.
 Photo © 2009 Dr. Mark S. Brunell.

            

The Native Americans also recognized the importance of the Mountain Alder and used it medicinally to treat anemia, internal bleeding, urinary problems, sprains, bruises, backaches, itches, dysentery, and hemorrhoids. They also used it as an emetic, a compress or wash for sore eyes, to cure saddle gall in horses, and when mixed with powdered bumblebees, to ease painful labors (Flora of North America).

When you take a peek around the valley this winter, many of the flowering parts of these alders look a bit strange. Clumps of curly, tangled, ribbon-like structures project from many of the cones- signs of the alder tongue gall.

Infected Mountain Alder near
the bridge at Basecamp.

The fungus Taphrina alni, originating from the geographical area of Austria and Slovakia, is one of the almost 100 species in the ascomycete genus Taphrina, which is characterized by its parasitic mycelial state on a number of vascular plants. One of the ways in which the species are differentiated includes their host plants (Rodrigues). T. alni specifically infects Alders, producing ‘tongue-like’ growths originating either from the bracteoles, in which case the growth points down, or the catkin ovarian tissue, in which case it points upwards. When the catkin is still green, T. alni develops as a flat projection and grows outward between the scales (Bacigalova). Throughout the season, the colors of the gall change with the trees, and remain hard and brown on the catkin until the tree drops them. T. alni spores are produced on the infected cones and are transferred via wind to other trees. While it has been stated that T. alni causes no measureable damage to Alders, the gall is persistent and seems quite widespread in the valley, warranting further research and observation before we can be sure (Wikipedia Contributors). 

T. Alni-infected catkin from an Alder at Basecamp

Catkins from an Alder at Basecamp
with minimal Alder Tongue Gall growths

Alder Tongue Gall projections removed from the catkin they grew on 

          

It will be interesting to keep watch on the Mountain Alders in the valley to see whether animals are less likely to eat seeds from affected cones, if the presence of the gall increases over the coming years, or if the gall causes any other changes to these trees that are so important to our ecosystem.  

REFERENCES

Bacigalova, K., Lopandic, K., Rodrigues, et al. 2003. Phenotypic and genotypic identification and phylogenetic characterisation of taphrina fungi on alder. Mycological Progress. 2(3), 179-196. doi: http://dx.doi.org/10.1007/s11557-006-0056-1

Ellis, H.A. 2001. Cecidology. 16:1.

Featherstone, AW. Species Profile: Common Alder. Trees For Life.     http://www.treesforlife.org.uk/forest/species/alder.html

Filip, GM, Parks, CA, and Starr GL 1992 Incidence of Wound-Associated Infection by Cytospora sp. in Mountain Alder, Red-Osier Dogwood, and Black Hawthorn in Oregon. Northwest Science.

Flora of North America Editorial Committee, eds. 1993+.  Flora of North America North of Mexico.  16+ vols.  New York and Oxford.

Tree Species Compendium, Tree Species BC. http://www.for.gov.bc.ca/hfp/silviculture/Compendium/MountainAlder.htm

Rodriguez, M.G. & Fonseca, A. 2003. Molecular systematics of the dimorphic ascomycete genus Taphrina. IJSEM.  53: 607-616. doi: 10.1099/ijs.0.02437-0

Wikipedia Contributers. 2012. Taphrina alni. In Wikipedia, The Free Encyclopedia. Retrieved January 14, 2013, from http://en.wikipedia.org/w/index.php?title=Taphrina_alni&oldid=517446480