Gumming does not mean your tree has lost its dentures. Instead, it is responding to injury.
Unlike people and animals, plants do not have an active immune system. Instead, injured or infected areas are walled off to prevent further injury or the spread of infection or infestation. Gumming refers to the way a specialized sap, or botanical gum, oozes out of an injury site or canker to provide protection.
Gumming is particularly common among stone fruits, such as nectarine and almond, though is can also be seen on mango, citrus, and eucalyptus.
Causes of gumming
Environmental stress, mechanical injury, insect attacks, and disease can all trigger a tree to start gumming. This creates a protective barrier, as well as tries to push any invaders out. You can use specific details surrounding gummosis to identify the problem.
For example, gummosis caused by insect infestation or mechanical injury will often exhibit bits of bark or sawdust mixed in with the gum. Look for other damage around the gumming site: Do leaves look sick or chewed upon? Has the bark’s integrity been breached? Do you see discoloration under the bark near the gumming?
How to manage gumming
You can help your fruit and nut trees stay healthy by avoiding mechanical injuries, and monitoring for pests and diseases on a regular basis, along with proper feeding and irrigation. If you suspect disease, scrape some of the bark away from the area surrounding the gum. If you see discoloration or streaking, it is probably a disease that needs further attention. In many cases, diseases can be halted by removing affected branches below the infected area, just be sure to sanitize cutting tools between each cut.
If the gum emerges from circular holes and contains insect larvae, the tree is taking care of the problem itself, though further monitoring is a good idea.
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