Do you have any good referrals for tree care? I have a paper birch that seems to be having some problems. The limbs are turning brown and is dying from the top down. Wondering about insects or diseases? This tree is over 12 years old and is nice and large (would hate to lose it!) Thanks!
I would first recommend talking with a certified arborist. Pick someone from the list found on the Iowa Forestry Extension site. They will come to your property and make a diagnosis, but will not fix the problem. The good part about their service is they give you an unbiased opinion because they aren't selling anything. A certified arborist will most likely charge you for coming to your property though.
You could certainly contact any of the tree care service companies in the phone book, but they may try to sell you services you don't need and may not accurately diagnose the problem. The other option is to take a leaf sample and photos of the tree to the Polk County Extension office and they will pass it along to someone in extension that can answer your question. Good luck!