Stressed Manchurian Alder - mold on branch?
History: In November I posted (https://ask.extension.org/questions/435607) about damage two of my trees sustained from deer rubbing their antlers on their trunks. My Manchurian Alder came back completely, but it is now stressed. It has been sending up suckers at the bottom of its trunk. I do need to clear away plants that are too close to it, and I'm hoping that helps.
But I now have noticed what looks like white mold (?) growing on one branch. Only one branch. There are many black bees flying around under that branch. I noticed some flies too, but mainly it's bees.
Help. Thank you.
Ramsey County Minnesota
It is impossible to determine for sure from your photos but I believe you have scale, perhaps Scurfy scale or Cottony maple scale. Please look at the photo and descriptions of soft scales in this link and treat accordingly. Horticultural oil can be applied this fall. https://extension.umn.edu/yard-and-garden-insects/scale-insects-minnesota-trees-and-shrubs