Blue Spruce rust
One of our blue spruce trees looks like the first photo on this page: https://www.extension.umn.edu/garden/diagnose/plant/evergreen/spruce/needlesdiscolored.html I can’t figure out which of the problems listed on the page relate to that photo. The problem tree is literally surrounded by other bile slpruce with overlapping branches, some trees bigger and smaller, and none others have this problem. So I don’t see or suspect pests. We did just have an arborist our to inspect our burr oaks on other parts of our property that have BOB. We’ve treated the oaks with a fungicide and own the trunk IV equipment. Is this some kind of fungicide? What’s the treatment??? We’ve sent our arborists kids to college with all the BOB problems and can’t really afford to call him out for 1 pine tree. Any DIY suggestions would be appreciated!! Linda Kay
Stearns County Minnesota
I can't tell from the photos whether these spruce have Rhizosphaera needle cast or not. However, Rhizosphaera needle cast is very common among blue spruce in our area. If your trees don't have it, they will probably get it (as will your neighbor's).
I also cannot add more than what is in our references on this disease (which include treatment options). It will continue to make your tree look less and less attractive.
The best advice is this: don't plant blue spruce in Minnesota.
If you want a definitive diagnosis, someone will have to assess the tree on site. And that would be your arborist. As far as I know, there is no systemic treatment for Rhizosphaera needle cast, although there are fungicide sprays. But the diagnosis must be definitive to apply them. If the tree is badly infected with Rhizosphaera, I'd recommend removing it.