Disease
Generally, western red cedars are healthy trees, especially if you plant them in the right location. However, there are several fungal diseases that can impact stressed plants.
The first is fairly uncommon but incredibly destructive.
Butt and Pocket Rot
Caused by Oligoporus sericeomollis (syn. Poria sericeomollis) and Phellinus pini, butt or pocket rot is a form of heart rot that affects many conifers but is particularly destructive in western red cedar.
In fact, western red cedars are the only living host. Otherwise, these pathogens colonize dead wood.
As the name suggests, it causes pocket-like rot in the “butt,” or the part of the tree just above the roots.
It’s one of the major diseases of western red cedar, but it’s most prevalent in western North America, though it can be found in Europe and Asia.
The pathogens can thrive in both live and decaying wood, but they only breed on dead wood.
Usually, by the time you know anything is going on, the disease will be way too far along to do anything about it.
As such, prevention is key. Avoid wounding your tree, control pests, and remove nearby decaying conifer wood that can harbor spores.
Leaf Blight
Wherever western red cedars grow, leaf blight, sometimes called Keithia blight, can develop.
That’s because the fungus that causes it, Didymascella thujina, is endemic to all the same areas.
Unless you live in a warm, moist environment, it’s fairly rare. It’s more common in coastal, low-elevation areas of the Pacific Northwest.
Whenever the conditions are wet and temperatures above 50°F, the spores will be reproducing and spreading.
Symptoms start with pale patches on young leaves, followed by brown or black spore structures. Infected leaves may turn brown or gray and drop, often making the tree appear scorched.
Older trees are generally less at risk to serious damage, but seedlings can be destroyed.
The cultivars ‘Atrovirens’ and ‘Excelsa’ are most susceptible. If you live in an area where this disease is a common problem, avoid these cultivars.
To prevent infection, maintain good airflow with proper spacing, water at the base, and keep weeds under control.
If needed, treat with copper- or mancozeb-based fungicides during spring and fall, following label directions.
Yellow Ring Rot
Caused by Coniferiporia sulphurascens (formerly Phellinus weirii), yellow ring rot is more severe in firs, Douglas firs, and western hemlock, but can also affect western red cedar.
The pathogen spreads on wood, both living and decaying, so it can spread through roots or wherever wood chips, fallen branches, tree stumps, or closely-spaced trees exist.
Once a tree is infected, it will slowly decline, but you’ll only see the rot if you look at the roots or cut open the tree. The big risk is that the disease will weaken the tree.
While it’s rarely fatal in home landscapes, prevention includes proper spacing, prompt removal of infected wood, and avoiding planting within 200 feet of infected trees.
There is no cure, so focus on maintaining overall tree health.
Embrace the Tree of Life
They are gorgeous, sturdy, and long-lived. Western red cedars are such graceful trees with their lacy leaves and swooping branches.
I’m always in awe of them, whether I encounter one while on a walk in my neighborhood or while hiking in the forests near my house.
I have a towering tree in my backyard that I love to watch during breezy days because it looks like it’s dancing.
How do you plan to enjoy your tree? Is it going to be a focal point of the garden or will you plant a few as a visual barrier between you and a neighbor? Let us know in the comments section below!
And for more information about cultivating conifers in your landscape, check out these guides next:
