Trees in cold climates lose water to the dry air when they are warmed by the sun (direct and reflected) but have frozen roots, so can't replace lost water.
There are products like wilt-pruf and vapor-gard that in essence put a very thin layer of wax on the tree. Studies I've read are mixed about the degree of winter protection. Some indicate that it's ineffective, some that it needs to be repeated every few weeks, some that it needs to repeated after every rain or thaw.
Given that the main mechanism is solar heating, it seems to me that increasing the reflectivity of the tree would result in less heating.
The ideal material would be strong enough to last through the winter, could be applied at near freezing temperatures, be inexpensive for the materials, and not be harmful to the needles.
A lot to ask for.
A good answer would be one of:
Personal experience doing this in a cold long winter climate (I'm in Canada Zone 3 -- roughly equivalent to USDA zone 2, and our winters typically have snow on the ground from mid November to mid April)
Pointers to publicly accessible research papers.
Bordeaux mix is used to control at least one needle cast fungus in colorado spruce used at an 8:8:100 concentration, applied at bud break, and every two weeks during the growing season. It's also used for balsam fir, and some pine fungal needle casts. This indicates that lime as such isn't harmful to the needles, at least at low concentrations.
Images don't appear very white.
