I have a large, 30-foot Colorado blue spruce in my yard that I really love. In addition, I have a row along my driveway of smaller blue spruce. One of my neighbors commented that they weren't looking so good, and when I looked closely I realized they are yellowing and dropping a lot of needles. The large one has yellow and brown needles along the inner half of each branch all the way up the tree. It does not look good. The row of smaller spruce is also yellowing. What do you think it is and what can I do to help them? I do not want to lose them, are they dying? - Les, Sturtevant.
There are many diseases and insects that can affect the appearance and health of Colorado blue spruce, which is why we at UW-Extension rarely recommend them for the landscape anymore. They are beautiful trees when healthy, and make magnificent specimen and hedge trees, so I do understand why people continue to plant blue spruce, but when they get a little stressed and/or diseased they stop looking so great.
Yellowing may or may not be indicative of a serious problem. This time of year many of our evergreens will start to drop their needle-like leaves. This is just seasonal needle drop, and is perfectly normal. Pines, spruce, firs and even arborvitae will drop needles in the fall. The way you described the pattern of yellowing and browning is pretty much what we would expect for seasonal needle drop, although I am concerned by the extent of the needle drop your trees seem to be experiencing.
It could be that seasonal needle drop has been made worse by a lack of water in the latter half of the summer and into fall. Although we had excessive rainfall early in the season, the last couple of months have been very dry. And if your trees are planted close together this drought stress would be worse for those trees. As the trees get larger, they will compete with each other more and more for water and nutrients. I would recommend that you set up a drip hose to water them all once a week.
To know for sure whether it is a disease or insect that is affecting your trees, we need to see a sample. Please bring one or two small branches that show healthy green needles and the transition to yellowing and browning. We can look at the sample in the office for a preliminary diagnosis, but before we can recommend any potential chemical treatments we need to send the samples to the Plant Disease Diagnostic Clinic http://www.plantpath.wisc.edu/pddc/ for Dr. Hudelson to culture. This costs about $20, but it really is the only way to know for sure if it is a fungal disease, and which one it might be.
You can also access UW-Extension Garden Facts sheets on the web at http://hort.uwex.edu
that will provide more information about the care of evergreens, and beautiful pictures of all of their diseases.
UW-Extension master gardener volunteers serving as plant health advisers can help answer your questions at email@example.com or (262) 886-8451 at the Racine Horticulture Helpline.
Winter hours began Oct. 5, so they will only be available one day a week but will respond to e-mails and voice mail messages when they are in.