I have a Bing cherry tree that had a large branch that just died last year, and now I just noticed another branch that had sprouted leaves and bloomed is now dead. Also, we have several Douglas Fir trees that have died in the last year (several branches turn brown and eventually the whole tree dies). Does anyone have any idea what might be causing this? I don't want to loose all of my cherry trees.
I will attempt to answer the cherry tree portion of your question. I'm probably not the right person to take on the Douglas fir, and more information will be needed to answer that question properly. You might want to resubmit your Douglas fir question as a separate, stand alone question.
The most common cause for cherry branches, or trees, to die is a disease called bacterial canker. This disease is especially prevalent in the Willamette Valley where there is a lot of rain in the fall and spring, when infection is most likely to occur. You didn't say how old the trees were, nor provide any other information on symptom progression, so this is just a guess. Bacterial canker usually attacks young trees. There is another disease, with similar symptoms that attacks more mature trees, called Cytospora canker. Both diseases cause a wound on the branch or trunk and can eventually girdle the branch or trunk, causing every part of the tree on the distal end to die. Here are links to more information. http://pnwhandbooks.org/plantdisease/cherry-prunus-spp-bacterial-canker