Question

Blue Spruce Top Dorman   QUESTION: The top of one of our blue spruce trees has gone dormant (?) this year.  The tree is approximately 18' tall and 20 years old.  The bottom 3/4 has all new growth, while the top looks like an old green.  It doesn't seem to be dead.

I've researched blue spruce diseases, but the two most commonly mentioned come nowhere near what seems to be going on with our tree.

Do you have any idea what's going on?  We would really hate to lop off the top or lose the tree.  Should we just let it be and see what happens?

Thanks for any help you can give.

ANSWER: looks like maybe a insect has killed the top of the tree. There is a weevil that will feed on the top leader of conifers and will kill the leader. There are also bark beetles that will kill the top. Check and see if you can see any signs of pitch oozing from the bark of the trunk at the base of the off colored needles. You can try spraying the top trunk with an insecticide called Onyx or Merit. These insecticides will kill the insect under the bark.

Looks like a fairly young tree so the top if it dies can be pruned off and over time a side branch will become the new top. There maybe a slight crook in the main stem where the side branch was but over time this will not be noticeable.

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QUESTION: My husband checked for the signs you said to look for and nothing.  Any other ideas?

Answer
If there was no sign of insect attack then it more than likely a canker disease called Cytospora canker.  Cytospora canker is characterized by the dieback of individual branches, usually starting lower on the tree where the branches are the oldest. On rare occasions, the entire top of the tree may die first.

The fungus that causes cytospora canker lives on the bark of trees and causes no problem until the tree is stressed. It can readily infect wounds from pruning cuts and mechanical damage to branches, but trees do not usually begin to show symptoms until they are ten to fifteen years old. Cytospora canker on Colorado and Norway spruce trees is overwhelmingly associated with drought stress. There are no chemical controls for cytospora canker. Protecting susceptible trees from drought stress by supplying additional water during dry weather and pruning infected branches can slow the spread of the disease.

Pruning out diseased branches is the primary means of treating trees showing symptoms of Cytospora canker.  Prune at least 4-6 inches below any visible cankers. To minimize spread of the disease, prune only during dry weather. The fungal spores of Cytospora can be easily spread when conditions are wet. Fungicide sprays are generally not effective at controlling canker diseases.

I would prune the top out and let a side branc take over as the top. If you want you can go aheasd and let the top die first BUT this may let the spores of the canker spread. If you prune dip the pruners in to a bleach solution between cuts to stop speard.