Red alder tree disease

Asked January 24, 2020, 12:20 AM EST

I am dealing with a group of unhealthy red alder. The infected trees all have a a dead area on the south side of the tree (sun scold?). The scold starts at ground level to as high as 6 feet.The bark is black and cracked,in the infected area. The tree's bark is also bright red outside the blackened area. The trees have tried to heal them selves. The dead areas on some of the trees have a small white fruiting bodies coming from the dead wood on the tree (may be related or a separate saprophite). Old stumps are covered with mushrooms covered in a mushroom that looks like turkey tail ( again not sure if this is related). Please refer to attached photos to help. Could this be nectria canker? It doesn't have the typical growth patterns of a canker (cat face). Then the mushrooms would be a separate pathogen? Please help. If you ID the pathogen -please confirm if this is a disease if the site. Thank you

Oregon red alder

1 Response

This does not appear to be Nectria based on the shape and pattern of the dieback. https://pnwhandbooks.org/node/2090/print It does look more like collar rot, a Phytophthora disease that can cause problems in wet or irrigated areas. https://pnwhandbooks.org/plantdisease/host-disease/alder-alnus-spp-collar-rot-phytophthora-canker Is the area wet or irrigated? For a definitive determination on this, you can have samples tested for Phytophthora at the OSU Plant clinic. https://bpp.oregonstate.edu/plant-clinic

It also might be sun scald, which is a common problem with red alder. I would expect sun scald only on the south side, on stems that did not develop in open sun and were recently exposed by clearing or other changes that opened them up to hot sun. So if these trees were not recently exposed, that would argue against sun scald.

I suspect that the white fruiting bodies are not related to the cause of dieback, but rather are saprophytes colonizing the dead wood.

Another consideration is the overall suitability of your soil and site for growing red alder. Alder on low quality sites for the species are prone to a variety of problems. The heat and drought episodes in western Oregon over that last 5 years have caused many alder to die back or die altogether on marginal sites throughout the Willamette Valley area and foothills.

If you wish to follow up on this inquiry, please contact me directly via email.
Best, glenn.ahrens@oregonstate.edu