alanmercieca,
How were you able to survey "a lot of universities"? A good idea for what? I know folks paint trees for different reasons - some not based in reality.
I doubt it's being recommended for treatment of pruning wounds.
We used to use tree wrap instead of paint on trees susceptible to sun scald because after they reach a certain age (size) you can remove it.
There are 2 kinds of people - those that like the looks of trees with paint on them and those who do not.
I had a neighbor who liked the look and painted all his trees up to about 5 feet. It looked like s . . t. I hate it - it annoys me - so I notice it.
I understand there are certain infestations that might warrant it, but I doubt they are that far reaching. I went to Va Tech and I've owned several orchards and I know a number of folks involved in these areas of expertise. During my time at VPI I didn't see any of the test orchards with painted trees and the last time I was down there I didn't either.
Anyway, if painting trees was a good idea and being recommended by the extension services or many universities, I'd expect my local orchards to have at least some painted trees. I am, after all, in an area once famous for its orchards.
I also live in an area hit hard by the pine boring beetle yet don't see large valuable commercial stands of pine being painted. I simply doubt that it's being touted as a good idea by a lot of universities as no one seems to be doing it and contrary to many folks beliefs - farmers, etc. aren't backward, lazy or stupid and most are very educated about the things they grow and stay very current with what is being recommended as otherwise they loose the tiny margins they survive on - and they have the extension service to help make sure they know the latest research.
Again if it does a lot of good why aren't the national forests being painted or Yellowstone, etc. In '06 I rode my bike from Va to Alaska to Mexico to Key West to Newfoundland and back to Va. 25k miles and 4 months cruising and taking wildlife photos and I don't remember any painted trees. Not in the US or the forests of Canada. Shouldn't there have been lots of painted trees if it was a good idea? I've also been in 40 countries and other then a few small examples usually around a civic courtyard in Mexico or Nicaragua there just aren't very many painted trees; and there should be if it were a good idea.
Why aren't all the newly planted teak, etc. stands in Costa Rica and Panama, etc. painted? Etc. etc. etc.
I'm afraid I'd have to see these studies before I jump on that band wagon. and there'd have to be a lot more then one from more then one university.