We have a Douglas Fir pine tree in central Iowa that is approximately 20 years old and 20' tall. Over the years it has always seemed to be healthy. The trees that are near it are the neighbors three very tall dark green pines approximately 20' to 30' away. There is a 6' pine approximately 40' away. There is also an ash tree approximately 40' away. All trees appear to be healthy except for the Douglas Fir and the 6' pine tree. The problem started last Fall and looks the same this Spring. The Douglas Fir has lost the pine needles on the outer edges of the branches to where they are totally bare up to approximately 5' high. The 6' tree is not a Douglas Fir (unknown). The original needles had decreased to about 1/2. However, the ends which are the new sprouts look thick, healthy and green for approximatley 1" to 2" long. Last year we had a lot of rain in the Spring with minimal rain the remainder of the summer. We also have had very little snow this winter. Any help would be greatly appreciated. Thank you, Cook