I read on another post here recently someone was having problems with Laubwerk trees producing fireflies and remedied the problem with adjusting the sun’s specular affect settings. (i looked for the thread but couldn’t find it again.) I had the same problem, and when looking through the 50,000 materials that laubwerk puts into the scene, I noticed that the leaf material reflection settings aren’t looking good. The reflection color value was almost 100%, and glossiness was .92. Both values way too high. I dont think these are fireflies as much as they are just overblown reflections. Good news is you only need to adjust the leaf material for the season of tree your using. I adjusted the reflection settings closer to what I think a leaf should be - I reflection amount around 33% and about a .75 for glossiness…I think 1.6 fresnel is fine…and trees looked good. I dont understand why there is an extra diffuse layer on top…but I’m no materials expert… Gonna try to remember to shoot Laubwerk an email to see if they can update their materials to work better with Vray 3.4. Also noticed the ‘linear workflow’ option is checked in their materials…but thats a whole 'nuther thread… 
On a side note - I was on a deadline (always on a deadline…) and didnt spend a lot of time experimenting with settings…so would love to hear if anyone gets better results with some other values. Also, if there is a way to change the materials once and for all wherever Laubwerk is storing the main files? (again, probably need to contact them about this…) (should also add…Laubwerk is really awesome…Laubwerk + Skatter has totally changed how we’re working in Sketchup) 