Ganoderma is just one of over 1,000 species of wood-decaying fungi. It is a soil-borne fungal disease that attacks the roots of trees, causing severe decay; generally the infection begins at a wound site. The disease can be spread to other trees that are in the same area as an infected tree through root contact. The ganoderma fungus remains active in the soil and in the roots of infected and dead trees.
This fungal disease can be caused by several ganoderma species: G. lucidum, G. applanatum, and G. brownii. According to Cornell University, “G. lucidum is rarely seen on forest trees, but common on maples (and other trees) in urban environments.”
Signs of Root Rot
Trees that have been severely infected with ganoderma root rot may appear less vigorous. However, in most cases the only sign that the tree is infected is when fruiting bodies or conks appear at the base of the tree. These conks become shelf-like as they grow-they have shiny reddish/purple tops, and the edges and undersides of the fungus or fruiting bodies are cream-colored. They can also grow from the roots of an infected tree, and you may see them in the soil around the tree.
Trees that have root rot are very often blown down during severe wind or rainstorms. You may not have even been aware that the tree was infected with ganoderma root rot-it will simply be blown over during a storm. However, after the tree is blown down the root damage will be apparent-the anchor roots will show signs of severe decay.
Prevention of Root Rot
Since there is no known chemical treatment for trees that are infected with this disease the best strategy prevention. Take care not to wound trees since infection can begin at the site of a wound, and keep trees stress free by watering during drought conditions. Maintain a program of proper cultural practices. Also, if you are doing any landscaping/construction in the area, avoid cutting the roots if at all possible. The University of Illinois also suggests, “Make as few changes as possible in the soil grade or drainage patterns in the vicinity of trees. Avoid compacting soil over the roots.”
Good Cultural Practices
Maintaining a program of proper cultural practices includes fertilizing the tree in late fall or early spring, deep watering during hot/dry weather, and proper pruning. Prune away any dead, diseased, or damaged branches as soon as possible. Pruning to maintain size within your landscape design should be done when the tree is dormant.
If you do have a tree that has been infected with ganoderma root rot and it has succumbed to the disease it is important to replant a tree that is not susceptible to this disease. (The fungi survive in the soil and in the roots of dead trees.) Also, be sure to purchase and plant healthy specimens.