I encountered the same problem with the nvidia plugin for photoshop, I'll give you the solution ,juste do not export trees with the photoshop plugin, exports then in png and made a conversion with DDS Converter 2, but before that check the option "Save Alpha (if any)", finally you can see the result .
I hope you can understand, and sorry for my bad english .
very good, but you have little problem with trees, I mean problem with edges, it's look like a old trees edges.
me too with my trees i have 10 15 % increase time of loading cause of 4096p.
but its not problem for me i can wait for loading for this beautiful textures .