Gummosis – On Peach, Cherry, Plum
Q: What is happening to my plum tree? It finished bearing plums in July and now the trunk is a sea of sap! Should I do anything?
A: I think it’s gummosis, a condition that’s very difficult to control on a single tree. Most often it is caused by stress or possibly by bacterial or fungal canker.
Stress could be from drought stress, certain viruses, adverse growing sites, winter damage, herbicide damage, wounds, bruising of stem tissue, etc.
Gummosis is a general, though nonspecific condition of cherry, peach and plum trees (both fruiting and flowering) in which gum is exuded through the bark. Gum is produced in response to any type of stress, not necessarily a wound, regardless of whether it is due to insects, mechanical injury, drought, cold injury or disease.
To that end, in the absence of a soil test, sprinkle 1 cup of garden lime per inch of trunk thickness under the branch canopy every year for three years. This will raise the soil pH, which peaches/cherries/plums appreciate.
Water the tree appropriately in summer so the roots are not damaged by drought.
Gummosis can also be caused by an attack by borers. In my experience this is rare, but examine the gum to see if any wood particles are in it. If there are several small pieces of sawdust in the gum, call your local Extension office (1-800-ASKUGA-1) for advice.
Here’s a good article on bleeding cherries
see also Gummosis