Identification

• Gray mold is caused by the fungus Botrytis cinerea, which attacks woody and herbaceous plants, according to the University of Illinois Extension. Severe infection can kill affected oak trees. Gray mold is spread from tree to tree by spores which are carried on the wind to susceptible hosts.
  
  

Symptoms

• The symptoms associated with gray mold include brown or gray webbing and the death of leaves, buds, twigs and new shoots. Using a magnifying glass allows the clusters of spores to become visible. Symptoms are most severe during periods of high humidity and wet weather.
  
  

Control

• Avoid applying water to oak tree foliage infected with gray mold, as this may worsen symptoms. Sanitation is extremely important in controlling the spread of gray mold and plant tissue infected with this disease should be burned or buried, states the University of Illinois Extension.