Douglas Fir with Blueish Sap?
Several mature Douglas Firs in my neighbourhood (Central British Columbia) are weeping a distinctly Blue sap this spring? Never seen this before, we've had an odd late winter early spring as temperatures were +10C one and 2 weeks ago, now they are -10C (April 1)
Outside United States
I would refer you to another answer on this site: https://ask.extension.org/questions/337091
Thank you Cindy for your response. I was confused why the pitch was a bluish colour this year and knowing that Mountain Pine Beetle attacked Pine trees often have blue stain fungus made me think of that. We do have Douglas Fir beetle at an endemic level in the Cariboo, but I couldn't see pitch tubes or frass with the 2 trees that had the blue coloured pitch. The tree in the picture looks healthy other than a couple of scars.
I consulted with a few of my collegues, an insect and disease and another forestry specialist, and this is what we came up with. It is fairly commonly seen on spruce and sometimes Douglas-fir. It likely is mostly white in color but in certain light appears blue. For spruce it occurs when the stem is attacked by Cytosphera fungus and something similar may occur on DF. Aside from that, the chemical composition of pitch may vary by genetics and soil nutrition. We haven't seen it on ponderosa or lodgepole pine - where we most commonly see pitch. We don't believe the color to be any indicator of a specific problem to the tree other than the injury that is causing the pitching.