By Naylor891
Colorado,
United States 
I have a mountainash tree that has these clumps all over the tree. Is this a disease or just a normal thing the tree does. I have since uploaded some more pictures. Hope they are better. Since I last ask the question I seed these clumps are dying and turning brown and dropping off tree. Mostly what I've learned this tree is not a Mountain Ash as I had thought. Whatever it is it's still a beautiful big tree.
29 Jun, 2018
Answers
Can't see it very clearly but it could be a cellular mass type growth.
29 Jun, 2018
It looks more like a true ash than a mountain ash, to me. If so, they could be the male flowers.
30 Jun, 2018
It doesn't look like a sorbus (perhaps only whitebeam) or fraxinus to me either. So I would think that it's a virus or flowers on a tree common to the US.
30 Jun, 2018
with Naylor being in the US I assumed mountainash was a common name for another species other than sorbus. So yes could be flowers
a photo with the light from the front rather than backlit would help.
30 Jun, 2018
As it appears lower down on the thinner branches and not the ends, which would be the case with flowers. I would say that it is an infestation similar to witches broom or mistletoe. You can cut out the offending growth.
2 Jul, 2018
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Could be a clump of lichen or a type of gall or a paper nest of wasps/bees.
could you take a close up of it.
29 Jun, 2018