Ask-a-Dave's-Gardener: Dawn redwood disease, 2 by dr8080

dr8080 wrote:
Hello,

My dawn redwood (potted) is starting to get a disease. These black dots do not move if I touch them. They have a little sheen to them in the sunlight and they wash off but underneath the needles are damaged. Some areas have thin web-like things in between the needles to which more black dots are stuck. Any idea what this is and how to control them? So far my only control attempt has been to cut off the affected branches. If I do not do this, the black dots typically spread down the branch.

Thank you!