Gummosis is the oozing of sap from wounds or cankers on fruit trees. It can result from environmental stress, mechanical injury or disease and insect infestation. Cytospora canker or Valsa canker, the fungal cause of gummosis, affects stone fruit trees like apricot, cherry, peach, and plum.
Cytospora infection is distinguishable from insect damage and mechanical injuries because sawdust or pieces of bark are not mixed in the sap, as it would be with insect or mechanical damage. Cytospora canker is also known as perennial canker. The oozing sap from fungus, bacteria, physical damage (lawn mowers, weed eaters, hail, etc.) or environmental stress will be amber and opaque.
Gummosis caused by peach tree borers will be mixed with frass created by the insects.
The solution for any of these situations and resulting gummosis is to get the tree back into a healthy condition. The entire Sick Tree Treatment needs to be applied with the root flare being the most important step. Tree trunk Goop should be applied to any wounds or cankers.