Black sooty mould on lower oak branches

I have 3 30 year old oaks that I grew from acorns. Only the largest is subject to black sooty mould, and its lower branches branches have retained last years sooty mould despite a very wet winter. I cannot remove it with my fingers. Has anyone nyone had success cleaning it off? Please let us know how you did it

I’d be interested to see a photo of it @hanshan. I have an oak (Q. robur) with what I once thought was sooty mould on its branches. However, I since changed my mind, considering that I’ve never once seen the leaves on this oak affected by sooty mould and that the black deposits didn’t simply wash off (as sooty mold is said to).

Instead, I suspect it to be a black epiphytic crustose lichen. Possibly Scoliciosporum umbrinum, or a species of Buellia or Lecidella – Whatever it is, I’ve come to really like it and feel it adds a nice quality of age to the tree and doesn’t appear to negatively affect its health in the slightest.

Try water and a toothbrush, but if yours is still not washing off, could there be the possibility that your tree is subject to sooty mold AND has a similar kind of lichen to mine on its branches? The stuff you’re having difficulty removing being the latter that remains?

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Really helpful info, thank you. I have never seen aphids or ants on the tree…but there are thin tracery lines of black on other parts of the tree. I will try using a brush and water to remove any possible black sooty mould, and I will try and send a photo to see if it is like the stuff on your oak. Thanks again.