Hello. I live in Junction City, Oregon and have pine trees in our forested area that are turning orange from the underside. The orange is visible well up into the tree now. My internet search leads me to consider this may be Dothistroma pini. What should I do? Can it be treated or should we remove the tree from our forest area?
Lane County Oregon
Thanks for your question about your pines. There are several needle blights that can affect pines (and dothistroma pini, described here is one). But without knowing exactly which type of pine you have, seeing a photo--up close and personal--of the needles and the entire trees, and potentially having the needles and the soil tested, it's impossible to tell the exact pathogen. This table illustrates just some of the ailments that can befall pines.
So, if you'd like to send some photos, I can help work through it a bit further. Or, you could take some branch samples (and your tree photos) into the Lane County Extension office (996 Jefferson Street, Eugene; phone (541) 344-5859) They may suggest you send needle and/or soil samples in to the OSU Plant Clinic.
So, can't suggest treatment or removal until these questions are answered. Good luck!