Sitka spruce turning brown
Lincoln County Oregon
Thank you for your questions about your Sitka spruce that has branches turning brown. I appreciate the clear pictures of the symptoms that you sent along.
It's difficult to diagnose an issue without seeing conditions up close and personal, but based on your pictures and the conditions and symptoms you described, I would not be concerned about your tree. Overall, your tree has a healthy-looking canopy, with full branches and ample foliage. Near the top on the upper right side of the tree, there is some evidence of thinning, and this may be due to winds and other environmental factors. While looking over the dead/dying branches in the photos, I also noticed some signs of localized defoliation on some of the branches.
It's my hunch that you have had some localized feeding by a defoliating insect, and perhaps some other insect-feeding damage (perhaps aphids or mites) on your tree. Also, some of those branches are in shaded out areas and in the lower half of the canopy. Sometimes branches under these conditions are more prone to dying, either through lack of resources like light, insect attack/feeding, or foliar diseases like rusts. To me it looks like you have a very typical-looking coastal tree!
Keep an eye on your tree and monitor the conditions through spring. Note any changes in condition. Your pictures are excellent, so be sure to keep documenting what you are seeing. Stay in touch with me, your Extension Forester in Lincoln, and I can help you with the information and resources you need, including next steps should symptoms intensify.
For your information, there is a great OSU Extension publication available to download for free called the Common Insect Pests and Diseases of Sitka Spruce along the Oregon Coast. It's a good resource to have and there are some very useful tables at the end that describe common damaging agents, from environmental conditions and human-caused damage, to insects and diseases. You can access the publication here: https://catalog.extension.oregonstate.edu/em9105
Thank you, and best of luck to you and your tree!