The client has a large oak tree that is losing sap. There is a bad odor and a hole at the base of the tree where sap is oozing. What is causing this and how should it be handled?
DIAGNOSIS /RECOMMENDATION
The problem is termed bacterial wetwood/slime flux, which is caused by various bacteria in a wounded area and is not uncommon in larger shade trees. If the tree is otherwise healthy, it should not be a serious problem. However, if the tree is under stress from other factors, it can move into the heartwood and eventually kill the tree. There are no controls for this problem nor can it be prevented; just continue to monitor the tree and minimize stresses and make sure to follow proper pruning practices. (1, 2)
ADDITIONAL INFORMATION
Generally, this problem is caused by common surface-inhabiting bacteria or yeast fungi that invade wounds and live off the nutrients in the tree sap. The sap eventually is forced out the wound by pressure from gases produced by the microorganisms living in the sap. (2) The odor is due to the fermentation process. Bacterial wetwood is noticed externally when it exudes slime and leaves a stain on the bark (3) Wetwood often supports large populations of bacteria from multiple genera, none of which are known to possess any host specificity. Wood harboring these bacteria has a strong, pungent odor and can range in color from pinkish, yellow, olive-green, to dark brown. (4)
Wetwood bacteria are both free living and common in soil and water. They must invade trees to establish but there is no evidence that this process causes necrosis to any live tissues in the roots, main trunk or branches. However, once established, wetwood bacteria colonize the heartwood tissues where they may persist for decades without ever causing any harm to the tree. Wetwood bacteria do produce enzymes that can degrade primary cell walls and other intercellular material, causing some weakening of the wood. But, they lack the ability to cause decay that would result in reductions in wood density. (4)
From The Bedford Extension MG Help Desk – July 2020 By: Betsy Brown, Bedford Extension Master Gardener Volunteer; Help Desk Coordinator
RESOURCE LINKS
1) https://extension.psu.edu/bacterial-wetwood-or-slime-flux (Note: copy and paste link into browser)
2) https://extension.umd.edu/hgic/topics/slime-flux-and-wetwood
4) https://ag.umass.edu/landscape/fact-sheets/wetwood-slime-flux
All resource links live and accessed, June 9 2020)