I’ve been watching my neighbors’ Austrian pines’ leaders turn brown for at least a year now.  I’ve seen this phenomenon elsewhere in the zone and wondered what it was all about.  The Plant Disease Diagnostic clinic here at Montana State University – Bozeman (where I used to work) just put out a press release that says they suspect it’s a fungus that causes a disease called blue stain.  This disease is also found in trees killed by mountain pine beetles.  Another suspect is a fungus that attacks the roots.  Many of the trees with dieback are planted in lawns where they may receive too much water and fertilizer. 

Earlier recommendations were to remove the tops, cutting well below the dead area.  But as we continue through the seasons, it appears the trees continue to die from the top down.  Unfortunately, the diagnosticians tell us, there is nothing that can be sprayed onto the tree to kill the fungus and save the trees.  They say it’s possible that there is a root drench that might help, but there’s no scientific data to support this.  (This treatment should be done by a certified pesticide applicator who specializes in trees.)  It’s recommended you not replace dead trees with more Austrian pines. 

Please keep in mind that ornamental trees in the landscape, as opposed to fruit trees, need little to no fertilizer.  Overfertilization can cause lush growth that is more susceptible to diseases and pests.

I feel badly for my neighbor who is losing her trees, but maybe it’s sweet revenge on some level – she’s been whacking away on her side of our cotoneaster hedge and spreading fireblight like crazy, and we may end up losing our  hedge!