Brittle Cinder Fungus

Overview

Brittle cinder fungus (Kretzschmaria deusta) is a soft rot fungus (Ascomycota, Xylariaceae) that causes the decay of buttress roots and the lower trunk of trees. The common name refers to the burnt or scorched appearance of the disease in its sexual stage. Common hosts include beech (Betula), maple (Acer), linden (Tilia), and hackberry (Celtis). However, the fungus has also been found on oak (Quercus), hornbeam (Carpinus), elm (Ulmus), tulip tree (Lirodendron), black gum (Nyssa), ash (Fraxinus) and other hardwoods. 

Symptoms and Diagnosis

Brittle cinder fungus typically manifests as irregular patches (stroma) along the lower trunk of a tree, often close to the soil line. In some cases, it may extend several feet above the ground along a crack or groove in the tree. In spring and early summer, the disease enters its asexual stage and is a light gray color with a whitish border. The fungus may also exude clear to amber-colored droplets. The remainder of the year, the fruiting body appears as a bumpy, blackened or charred crust (sexual stage). The crust has a "crisp" sound when broken off and crumbles easily when crushed underhand. The fruiting bodies persist on the bark and can expand in size in subsequent years. 

The disease attacks both cellulose and lignin, but primarily degrades cellulose. This causes the wood to lose strength and become brittle, leading to the potential for breakage and sudden tree failure. It is difficult to asses the extent of internal decay just from the presence of the disease. An infected tree can have a full crown and appear healthy, but have advanced internal decay. There is no effective treatment for the disease. 

Identification of the disease should be conducted by an expert, as its appearance can be mistaken for other fungal diseases (i.e., Hypoxylon/biscogniauxia canker). It can also be easily overlooked, as it does not produce typical fungal fruiting bodies such as mushrooms or conks.

Life Cycle

Brittle cinder fungus is dispersed by airborne spores and often infects trees via wounds at the base of trees, such as those caused by string trimmers or mowers. There is some evidence that the fungus can also spread via root grafts. Decay progression is strongest in weakened trees. 

Integrated Pest Management Strategies

1. There is no effective control for the disease. Once a tree has been infected, there is no way to treat or slow the spread of brittle cinder fungus. The tree will eventually succumb to the disease. 

2. Submit samples and contact a Certified Arborist. If you suspect your tree has brittle cinder fungus, submit a digital or physical sample to a diagnostic lab for confirmation. If the disease is confirmed, a Certified Arborist can help evaluate the tree and provide options. 

3. Maintain tree health and minimize damage. To reduce opportunities for fungal infections, keep your trees healthy through proper watering, pruning and fertilizing. Protect trees and prevent any damage to the bark, buttress roots, or root system caused by mechanical equipment. 

Organic Strategies

Strategies 1-3 are strictly organic approaches.