Blue Spruce Diseases and Remedies.

Courtesy of gonczol at sxc.hu.

I have two wonderful blue spruces in my front yard, and I would guess their age at about 30 years old and about 35 feet tall. They have been living happy, healthy lives until last summer when we started to notice the needles falling off the taller tree. After a little digging, I found a few answers.


The Diseases:
According to Iowa State University, diseases in blue spruce are rare, but when it occurs, it is usually one of two issues.


Cytospora Canker
 Cytospora Canker is a fungus that usually attacks older trees, or trees undergoing environmental stress. Extended periods of drought or extreme temperatures are factors with this issue. My best guess is that this disease causing the problems with my spruce, and it showed its ugly head as an after-effect of the 2010 blizzard an our constant-yet-necessary pruning. The fungus enters the tree through cuts or broken branches. It spreads and if left untreated it inevitably kills the spruce.


What to watch for:
White sap shows on branches as the tree attempts to defend itself. You will also see the browning of needles and eventual die-off of entire branches, which will start at the bottom of the tree.


How you can help:

During dry conditions, prune affected branches back 4-6 inches from infected site. You may need to remove whole branches to do so. Also, basic garden and tree maintenance helps with the prevention of this disease. This includes planting trees in roomy, well-drained soil, spreading mulch around the trunk base,and keeping the tree properly watered.

Rhizosphaera Needle Cast

 This is a very long name, so I am shortening it to "RNC." RNC is similar to Cytospora Canker in that it is a fungus which effects can be seen in the needles and it works its way up from the bottom branches of the tree. The needles turn a shade of purple and then brown and, if looked at closely with a magnifying glass, you will see linear black spots. These spots are the spores of the fungus growing on the spruce. This fungus can spread from both needles on the tree and fallen needles and usually shows up during unusually wet conditions. This illness is more common than Cytospora Canker.


What to watch for:

Discoloration of second-year needles and needle fall-off.


How you can help:

A fungicide regimen can help rid the tree of disease. Iowa State University suggests "Daconil 2787, Daconil Ultrex, Terranil 90, Thalonil 4L, Thalonil 90, Manicure Flowable, and Twosome Flowable" as the fungicides of choice, but please read the label to make sure it covers Rhizospaera fungus. Spray the fungicide the last 2 weeks of May and again 4 to 6 weeks later. Be sure the read the label for proper application. 

Again, basic garden and tree maintenance helps with the prevention of this disease. This includes planting trees in roomy, well-drained soil, spreading mulch around the trunk base,and keeping the tree properly watered.

Best of luck with your spruces!