Answer: Your question is really more involved than I can adequately answer in this forum. I would suspect bark beetles doing the apparent damage but they typically attack trees that are otherwise under stress. The soil moisture level may be the stress factor, but often mature trees will either suddenly show signs of water (or insect or disease) stress, or they will endure the stress and decline slowly over a period of months or years. I cannot tell you what might be ailing your trees, but I can recommend you contact a local expert. Contact:
Associate Professor and Extension Educator - Forestry/4-H/Agriculture
UI-Clearwater County Extension Office
2200 Michigan Ave.
Orofino, ID 83544
Professor and Area Extension
Educator - Forestry
UI-Kootenai County Extension Office
UI Coeur d'Alene Center
1000 West Hubbard Ave., Suite 140
Coeur d'Alene, ID 83814-2277
Either should be able to answer your question or direct you to someone who can.
Best wishes with your pine trees!
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