In addition to my previous post.
I made a quick Internet search and apparently painting tree trunks is rather popular in many countries with hot climate for the same reason (fighting sun burns and insects).
Mexico (there are accounts of seeing painted trees even in forests):
Orange grove in Turkey:
An article on ehow.com about paining trees (with reasons and explanations):
I believe it's possible to find similar examples in some other countries with colder, or to be more exact with acutely continental climate.