Ask Extension - plum tree disease (Trees & Shrubs)

From: Greg Stack
Extension Educator, Horticulture
Matteson Extension Center
gstack@illinois.edu

The pictures you sent are that of that a disease called perennial canker or gumosis. This disease is common in stone fruits and attacks trees that are either under stress from drought or fertility or both and are presiposed to the problem due to winter injury (cold). There are no effective sprays. The best thing to do is to try and maintain the tree in as active and vigorous stage of growth as possible. This means making sure the tree recieves water during drough and not fertlizing late in the season. Fertilize in the spring. Also if there are cankers on small limbs these can be removed by pruning those limbs off going back 3-4 inches past the cankered area and back to a appropriate branch angle. If they are on main limbs or the trunk you could remove the cankered tissue with a pocket knife cutting an inch or so beyond what you see affected cleaning up all damaged tissue. There is no need to go deep into the heartwood. Also with good clean cuts no need to apply tree paints. Do all of this when it is relatively dry and no chance of rain for a while. Again tree vigor is the best defense against this.

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