Spruce problem

(Question)

I have a large spruce tree in my back yard in Toronto, which must be at least 30 feet high. The tree is over 20 years old and back yard faces south. It has been very healthy for all those years, but now there is a problem. The problem has been rapidly increasing over the last several few weeks, the branches are turning yellowy brown in various places – in the centre of various branches. I have been trying to figure out what is happening. I fear it is Cytospora Canker as there is what appears to be white sap leaking down the tree. I have been reading that there is no cure for this, but I also read something about a treatment which involves a systemic trunk injection of a fungicide to stop the progression. Is this possible? I would hate to lose the tree. A picture is attached. Thank you.

Brown spruce needles

(Answer)

Looking at your photo, I am guessing you have either a Picea abies (Norway Spruce) or a Picea pungens (Colorado Spruce).

At this time of year there is a natural autumn needle shedding process that occurs in evergreens. The loss of older interior needles in the fall is often confused with injury, disease or insects. This process usually goes unnoticed since the needles on the inside of the conifer are concealed by the foliage on the exterior of the tree. Leaf drop on evergreens usually takes place gradually, but there are occasions when many leaves will discolour simultaneously, and the tree or shrub may appear to be dying.

Environmental stress factors also can play a role.  Although difficult to prove definitively, factors like sun scorch, wind and drought can cause a tree to shed needles.  Signs of live buds and green tissue in new stems are an indication that the tree is still healthy. The tree may need supplemental water this season and in periods of drought. Other noninfectious problems that can mimic disease are such things as an imbalance in soil pH, poor fertility, fertilizer or chemical burn, root injury, root rot, drought stress, and spider mite infestations.

Both spruce types are susceptible to Cytospora canker which involves browning needles and the leaking white sap you have described.  From your photo,  it looks like this is what is affecting your tree.  According to the Missouri Botanical Gardens, the needles turn brown and after a few months drop off and white or light blue patches of resin become obvious on the dead bark of larger branches. As the disease progresses over several years the higher branches are also affected. The dead area are referred to as cankers and as they enlarge and girdle the stem, parts above the diseased area lose color, make little growth, wilt or wither, and die back from the tips. The resin exuded from cankered branches is visible on dead bark after infected needles are cast. This is the most obvious symptom on infected branches.   If this is what is affecting your tree, they suggest the following:

  • Prune out the diseased branches in late winter when it is sunny and the trees are dry.  Clean your tools afterwards.
  • Water during dry periods, aerate the soil around the tree to relieve soil compaction and facilitate water and nutrient penetration.
  • Fertilize to maintain vigor.
  • Maintain good air circulation.
  • Fungicidal sprays are seldom effective and are not recommended.  Consider using fungicidal sprays only if the tree is very valuable and you are willing to pay for regular sprayings.
  • Remove the infected tree and plant a different species or variety.

Should you wish to do some further research of your own, a useful diagnostic guide from the University of Illinois can be found at:

http://hyg.ipm.illinois.edu/pastpest/200602a.html

And, from the same university, excellent diagnostic images:

http://web.extension.illinois.edu/plantclinic/downloads/Plant%20Clinic%20Report%20Spruce.pdf

Other sources:

http://www.missouribotanicalgarden.org/gardens-gardening/your-garden/help-for-the-home-gardener/advice-tips-resources/pests-and-problems/diseases/cankers/cytospora-canker.aspx

http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/agdex4144