Root rot  is a common problem with Atlanta trees and may only become evident when the tree falls during a storm. However, one surface indicator of root rot is the presence of mushrooms around the base of the tree.

The presence of the mushrooms do not mean the end of the tree but it does mean the presence of decay and make the tree a higher risk tree particularly when they are within target of houses or apartments. These mushrooms are called basidiocarps and thrive in a wet environment – which there’s plenty of lately.

Their color it is due to different fungi, which ultimately have the same rotting effect at the root level of the tree. They could be very large with a brown top (Inonotus dryadeus) or organge-maroon with a varnished top and very hard (Ganoderma lucidum). There are no studies that show that one pathogen causes a more severe condition than the other.

However based on studies the severity of decay can be estimated by:

  • Presence of basidiocarps;
  • Number of basidiocarps-the greater the number, the more decay;
  • Size of basidiocarps-the larger the basidiocarp of a given species, the more decay; and
  • Distribution of basidiocarps around the tree-the larger the percentage of the circumference found, the more decay.

In addition to the presence of basidiocarps, root rot caused by Armillaria spp. can be identified by the presence of white, fan-shaped mats of fungal tissue (mycelium) beneath the bark at the base of the tree or on larger roots, and by black, shoestring-like structures (rhizomorphs) that can be found beneath and on the surface of the bark and in the soil.

A positive diagnosis (presence of the basidiocarps), means that decay is usually well advanced at this time. The removal of the affected tree to avoid damage to surrounding property is what is recommended as blown-down trees can cause considerable damage to property.