Identification: ID of possible fungi on dawn redwood understock

Here is a possible fungi growing on the south side of the trunk that is filtered shade by surrounding plants. My wife noticed the growth yesterday while watering. When water hit the growth it completely flattened and is starting to bulge out again as the pictures were taken just now, 24 hour after first noticed. Any ideas what this is and if it is harmful or needs further attention. Thanks in advance for all your help!

 

It appears to be a crustose fungus or a slime mold. Is the wood under the thin crust material hard or soft?

 

Thanks for your response! The wood is hard under the thin crust. The mass has not changed since my last post. My wife did share that it was ball shaped and cream tan in color. After being hit by water spray it flattened and has the more brown tan color with brown spots like in the photos. Hope this helps and thanks for all your help!

 

It's probably a crustose fungus, but an exact ID will be difficult to get, since there are very few experts for this group of fungi. I'm not very familiar with them, but I understand that they are saprophytes and will not invade living tissues in the tree. However, the fungus appears to be established on some dead heartwood exposed where a large branch was cut off. If that is the case, then it may eventually rot the interior of the whole tree, weakening it considerably. If you value this tree, I recommend that you consult a certified arborist to get an expert opinion on what to do.

 

I agree with vitog that consulting an arbourist would be a good idea.
However, when you mention that water spray flattened it, that brings up the possibility, as vitog mentioned, of this being a slime mold. Slime molds are watery/evanescent, and some leave leave a thin crusty but still evanescent remnant when they are finished reproducing.
If you could clarify that would be useful, as a slime mold would not cause trouble for your tree. However perhaps there is a crust or polypore fruiting body underneath, which would usually be hard or leathery, and would not melt away at the touch.

As per vitog's comments, noting the part of the tree inhabited may help ID: Many species specialize in different parts of trees. Also they have different rates of decay: In some species a tree would be killed relatively quickly, with others this would take many decades if the main part of the tree remains strong.

good luck with your investigation,
frog