Gummosis is the oozing of sap from wounds or cankers on fruit trees. You can get it from environmental stress, mechanical injury, or disease and insect infestation.
Cytospora canker, or Valsa canker, the fungal cause of gummosis, affects stone fruit trees such as apricot, cherry, peach and plum. There is no known cure for Cytospora canker. The best approach in managing this disease is to maintain the health and vitality of susceptible trees. Vigorous trees are less susceptible to Cytospora canker, and if infected will slow the progress of the disease.