I haven't done that simply because I either spray trees/shrubs before they break dormancy OR if I spray them now I do 2 things.... 1) use clethodim & crop oil for the killing agent. (yes, I do have harder time of course if broadleaf problem present, in those small instances I'll get down with backpack spray with round-up and put on heavy dropplet volume to reduce drift & spray carefully, never have killed a tree). I use Atrazine, Surflan, Panoramic & Melachlor (dual II) for all season control of all weeds. 2) spraying high volume, I use gun on tractor with sprayer. I spray a U shape or full circle when safe enough. Even though I have clethodim & crop oil that's safe on trees, I still avoid getting them soaked. Done carefully, I can still cover about 3,000 trees per day doing that. Not sure on shield though, maybe some others have tried. Sorry on that account.
