I've had good luck fighting trees with WifiPlus antenna's. A little spendy but they do work. I use 1 of the 4 inch beams on my tower and managed to shoot through a 100 feet of tree's a mile and a half away from the tower.
I'm using a 200mw radio on tower and a Smartbridges Air Bridge Outdoor with the 18 inch beam on customer house. I show 90% link quality and 80-85% RSSI.
Hydro
OOPS forgot the web site
www.wifi-plus.com