Beech Bark Disease

• Beech bark disease is a fungal disease that attacks trees infested with the beech scale insect. The beech scale causes wounds in the bark when it feeds on the tissue underneath. These wounds allow the nectria fungus to enter the tree, forming cankers that may not appear for several years. The cankers are dead areas of tissue and, as they grow, they can completely surround the trunk, killing it. This disease can't be controlled when it appears in the forest, but scales on valuable ornamental trees can be killed with insecticides. Consult your local county extension for information about which chemicals are registered for use in your area.
  
  

Armillaria

• Amillaria root disease is a fungi disease that attacks conifers and broadleaf trees that are stressed by insect defoliation, drought or other environmental factors. Symptoms include the appearance of yellow-capped mushrooms that are 2 to 6 inches in diameter, growing at the base of the tree. Black fungal threads can be found under the bark on the lower trunk and along the roots. There is no way to control this disease.
  
  

Anthracnose

• Anthracnose is a fungal disease that attacks the leaves of susceptible hardwoods such as oak and maple. Symptoms include the appearance of small brown spots on the leaves. These spots grow bigger and form dead patches between the veins. The leaves may fall off the tree and the twigs and buds can die. Usually the leaves on the lower, inner branches are most affected. This disease is more severe when the weather is cool. Control anthracnose by pruning and destroying infected branches and by raking and destroying leaves. Fungicides are available for use in severe cases but otherwise they're not recommended.
  
  

Oak Wilt

• Oak wilt is caused by a fungus that attacks the vascular system. Symptoms begin with wilting and bronzing of leaves in the upper part of the tree. As the disease progresses, the leaves look water-soaked and turn brown along the margins. The tree then sheds most of its leaves and may die within a few weeks. Additional symptoms include branch dieback and brown streaks under the bark of affected branches. Red oaks are especially susceptible to this disease and should be removed and destroyed. White oaks are more resistant and don't need to be destroyed because spore mats don't form on them.
  
  

Powdery Mildew

• Powdery mildew is caused by several different fungi that cause a powdery white fungus to grow on the upper surface of the leaves. In addition, leaves can become twisted, wilt and die. This fungus can also form on twigs. Powdery mildew infections are worse when the humidity is high at night and low during the day, and when the temperature is between 70 and 80 degrees Fahrenheit. Powdery mildew doesn't cause much damage on trees so fungicides aren't needed.