Causal Agent

Stegophora (syn. Gnomonia) ulmea  

 

Hosts

Susseptible elms include American, Chinese, Dutch, Scotch, slippery, and winged varieties, and disease severity may vary from tree to tree of the same variety. 

 

Symptoms

Leaves and twigs with black spot begin with small, white to gray to yellow irregular spots which later become "tarlike" black spots. Leaves may turn yellow and exhibit premature defoliation. Usually the disease becomes prevalent in the fall about the time of normal leaf drop and little damage is done to the tree. 

 

Control

Infected twigs and dead limbs should be pruned and destroyed (buried or burned). Protective sprays are available and should be applied in the spring as leaves unfold. Please contact your local county extension office for current information.