What is this silver maple tree ooze and should something be done about it?

Asked January 7, 2019, 2:56 PM EST

Hello! I recently purchased a home in Bloomfield Township, MI with a number of older trees on the lot, specifically silver maples. This past fall, I had the trees dead wooded and trimmed. One in particular is a large silver maple, the trunk of which abuts an old paver patio on one side while the ground on the opposite side tapers down the yard. The tree trimmers brought to my attention that there is some rot in a 5" hole located off a large branch of the tree trunk and it was suggested to me to fill it with Great Stuff expanding foam. After doing a little research online, I did NOT fill the hole in the tree and opted to leave it open to the air. This afternoon, I found the 5" hole secreting an off-white/yellow ooze and a smaller hole on the main trunk doing the same. What is this ooze and does it require attention?

Oakland County Michigan trees and shrubs disease issues gardening horticulture

3 Responses

Thank you for sending a clear picture. The ooze or liquid you are seeing is called bacterial wetwood/slime flux. It is caused by several types of bacteria that enter pruning wounds, trunk cracks, V-shaped branch crotches and injection holes. The bacteria’s 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 and the liquid flows down the bark. As the slime flux dries, a light gray to white encrustation remain on the trunk. Many trees develop slime flux including elm, oak, and mulberry, and to a lesser extent maple, birch, butternut, redbud, sycamore, and walnut. It is not uncommon for this in older trees. There is no cure for this disease and it will not necessarily kill the tree but if the tree is under stress from other factors, wetwood bacteria can move into the sapwood and cause leaf yellowing, wilting and branch dieback.

It is best to monitor your trees this spring and summer for these and any other issues. Since this is a new home with many older trees you eventually may want to have an arborist out to make an onsite assessment. If so, you can find a certified arborist at the following website by using your zip code. Make sure they are certified since they are the ones with the education in all things woody.


I have included several links on wetwood/slime flux that you may find beneficial and kudos to you for researching what not to do in filling in tree holes. Using any material to fill in tree holes does not help the tree heal in any way. It does more damage than good as your research showed. For future reference when researching, go to an “edu” site. This is where you will find scientific researched based information by universities and other reliable sources.





I hope all this helps you out and good luck in your new home!

Thank you so much for the helpful information!