Identification

• River birch trees are susceptible to oak root fungus also referred to as armillaria root rot. The disease is caused by the soil borne Armillaria mellea fungus that infects and enters the tree through the roots.
  
  

Damage

• The fungus infects and starts to kill the water conducting or cambial tissues in the tree. Major tree roots and lower trunk area are the first to die. Visible symptoms include stunted and discolored foliage accompanied by premature leaf drop. Tree branches are the next to die, starting from the top. There are often clusters of mushrooms growing at tree base. The entire tree is eventually killed.
  
  

Management

• The fungus causing the disease persists for extended periods in soil and in old roots. Preparing the planting site well and removing all old roots from the area are among the recommended preventive measures for reducing chances of disease. Use only resistant varieties in areas with prior cases of the disorder.