Understanding Butt Rot: How Brittle Cinder Fungus Affects Trees

Kretzchmaria deusta (k. deusta)

"brittle cinder fungus"

Root and basal rot from the Kretzschmaria deusta (or “brittle cinder”) fungus can be a major problem in our area affecting a wide variety of deciduous tree species. We’ve personally encountered it mostly on maple, beech, oak, and hackberry. Brittle cinder is a destructive root and trunk rot pathogen which rapidly causes infected wood tissue to lose strength. The spores can spread by air into existing basal wounds or cankers, or otherwise through root grafts between susceptible trees. As with any pest or disease issue, stressed trees are typically most susceptible, so generally keeping your trees healthy and thriving is a great preventative management strategy!

Warning Signs:

1. Flattish or lumpy gray-colored fruiting bodies with white margins (typically seen in the Spring and Summer)

2. Same bodies mentioned above turn dark black in color, and bubbly burnt-looking pieces of the fungus can often be broken off easily and crumbled between your fingertips

3. Sometimes bleeding cankers will develop and can be confused with Phytophthora cankers (which are also common but treatable)

   

   Unfortunately, due to the unique decay pattern, this wood can still appear relatively sound as decay spreads through the roots and lower trunk! This makes trees infected with K. deusta particularly dangerous for climbing arborists, especially if infected trees are allowed to decay in place for too long. Arborists who know how to spot this disease may have to set up more complex climbing and rigging operations to protect themselves and your property during the removal of badly infected trees, or access the tree with a crane or other large equipment where possible. Inexperienced arborists who may not know how to assess for this fungus are especially at risk. Because the roots and base of the tree are affected, trees with brittle cinder fungus can become a significant fall risk onto your home or other nearby property! The best thing to do upon discovering a brittle cinder/K. deusta infection on your tree is to have it removed promptly, and stump grind as much of the root material out as possible. Fortunately, even though the disease is thought to spread by root grafts underground, it doesn’t seem to be particularly aggressive in this way. Removing infected trees and stumps is generally quite effective in halting the spread of this deadly disease to your other nearby trees!