Douglas Fir with Blueish Sap?

Asked April 1, 2020, 12:09 PM EDT

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

3 Responses

I would refer you to another answer on this site: https://ask.extension.org/questions/337091

Your tree has some pretty severe flow. Douglas fir are susceptible to rot and that is likely the problem with this tree. It looks to be along a crack in the tree. There is probably rot in the tree and the changes in temperature could have caused a frost crack in the already weaked fibers, now the pitch that is building in the tree has an opening to flow out as it loses pitch it is making more, and flowing more. Pitch has a different function than sap. Sap conducts nourishment through the tree where pitch is a defensive mechanism. Pitch can fill open areas within the tree, cover scars and wounds on the outside of the tree, and push beetles out. When a tree has a problem, pitch is it defence. As stated in the referenced article if a tree has a good crown and plenty of good holding wood it could continue to stand a long time. It is more at risk though for wind breakage. Being as it is in a park it could be a risk to keep. This could be a good opportunity to have some of those kids who play there be involved in the planting of a new tree and putting up some protection from the deer that might want to eat the needles and rub the tree with their antlers.

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.