Does my blue spruce have Rhizosphaera?

Hi Ozeruga,

Thanks for posting your question to the MyWoodlot forum! A few months ago, a forum user asked a similar question about causes of blue spruce needle loss. These extension articles discuss possible reasons for blue spruce needle loss, as well as treatment options for Rhizosphaeara:

New Mexico State University publication, Rhizosphaera Needle Cast Disease of Blue Spruce - has a good paragraph on Disease Management: aces.nmsu.edu/pubs/_h/H163/welcome.html

Purdue University publication, Why Spruce Trees Lose Their Needles - explains a telltale sign of Rhizosphaera, tiny black dots arranged in rows on infected needles: extension.purdue.edu/article/29053

Michigan State University publication, What's going on with blue spruce? - http://www.canr.msu.edu/news/whats_going_on_with_blue_spruce

Iowa State University article - Common Diseases of Blue Spruce http://www.extension.iastate.edu/harrison/news/...diseases-blue-spruce

I hope you find these to be helpful.

Kind regards,
Kris Brown

Thank you. I did notice upon further review some fungus on the tree. Any help of this maybe the cause or what type of fungus?

It's possible that it is Cytospora canker, in which case you can simply prune out the diseased branch when the wood is dry to avoid spreading it to other branches. Just FYI, I based my response to your question from these two articles: https://www.canr.msu.edu/news/whats_going_on_with_blue_spruce and https://www.canr.msu.edu/resources/cytospora_canker

Thank you Brown. Is there any type of fungicide i should spray against the fungus? I have been googling around for some products however nothing particular comes up.

If it is indeed Cytospora canker, this article (https://www.canr.msu.edu/news/whats_going_on_with_blue_spruce) says that there are no effective chemical controls. Here's a copy and paste from that article:

"There are no effective chemical controls for Cytospora canker. Avoid wounding lower branches with lawn mowers. A very important management tool is to prune out and destroy cankers as soon as they are observed. Prune only during dry weather to avoid spreading spores to healthy branches."

For now, I would try pruning out that branch with the fungus. The bottom line though is that you'll need to try to determine what is causing the needle loss/fungus. If you have a hand lens, you can look for round, black fruiting bodies sticking out of the tiny pore-like openings (stomata) on both green and brown needles. Apparently, this is indicative of Stigmina or Rhizosphaera, but you'll need an expert (not me) with a microscope to tell the difference (https://www.canr.msu.edu/news/whats_going_on_with_blue_spruce).

Wow, I'm in over my head here! I'm not sure where you are based, but if you're in New York, I'd try the local Cornell Cooperative Extension office. Also, see what you can learn from the articles I've shared. For example, it sounds like this summer, if it is something like Rhizosphaera, you should see needles turning yellow and reddish purple this summer (https://aces.nmsu.edu/pubs/_h/H163/welcome.html).