I've been using a 30:1 hose end sprayer to spray 12-16 foot trees at 60 psi... it's way too much at around 3 gallons per minute. Most all of what I have found for backpack sprayers are targeted for 'turf' use, not trees. I'm on residences that have electric access, are'nt there any portable 1gpm sprayers for trees that are reasonably priced and/or ac powered ?