Betty R. asks: What are these yellow mushrooms around the base of my oak tree and should I be concerned?
Answer: Wood decay fungi. There are several species that can cause root and butt rot in oaks.
Within the past decade there has been an increase in root and butt rot of old oak trees in North Carolina, especially in urban landscapes, parks and along streets. Although several species of oak have been involved, willow oak and water oak are the most frequently affected. These two oak species were commonly planted along streets and in the landscape in the early to mid-1900s, and normally live 65-80 years. These trees are succumbing to a variety of problems as they reach their life-expectancy.
Most oak species are susceptible to root and butt rot by the various species of fungi. The following oak species have been reported as hosts for the most commonly encountered fungus, Inonotus dryadeus: Quercus alba (white), Q. coccinea (scarlet), Q. nigra (water), Q. phellos (willow), Q. prinus (chestnut), Q. rubra (red), Q. shumardii (Shumard), Q. stellata (post), and Q. velutina (black). Older long-lived oak species (white and red oaks) and short-lived species (willow and water oaks) are most frequently affected.
Symptoms - Blow-down during rainstorms or windy periods is often the first and only indication of root rot. Sparse foliage with limb dieback also may be symptomatic of root rot but are not consistently associated with the disease prior to blow-down. Advanced decay of the larger roots, especially the tap or anchor roots, is evident after blow-down. Decay may extend from a
few inches to several feet into the butt portion of the tree, depending on the species of fungus involved. Decay may be of the white rot type, characterized by whitish to straw-colored, wet, stringy wood; or of the brown rot type, characterized by brown, dry, crumbly wood often with horizontal and vertical fissures.
Control - Prevention is difficult due to the longevity of the oaks and the locations where the disease is frequently found. The fungus enters the tree through wounds so any precaution that would reduce injuries to the roots or base of the tree is advisable. However, prevention of injuries over several decades in landscape situations is difficult or even impossible.
Prompt action upon diagnosis of the disease is paramount. Sometimes, removal of the affected tree to avoid damage to surrounding property is recommended as soon as possible. Blown-down trees can cause considerable damage to property.
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