...I think that may actually be due to shadow, as I didn't touch the WB in post...
Quite likely, as shadows tend to have a cooler WB by default. I sometimes leave it as such, or even accentuate it, if I can contrast it with the rest of the scene nicely (you know, the standard blue-orange complimentary color contrast generally works well). In this particular case, the upper left tree is placed inconveniently close to the rest of the scene that has a rather neutral WB.
For comparison, take a look at the lower right-hand corner: it also has the same bluish cast, yet is not that much objectionable, as a pretty large area around is in the shade and exhibits the same cast, plus it contrasts nicely with the oranges.
What I would do? I would either bring everything closer together (i.e., close to neutral WB) or I would cool the lower left corner as well, creating the impression that the whole foreground is in the shadow and thus cooler. The latter would also "push" the eye toward the middle ground and background.
