I spray a lot of weeds with Roundup around our place but I don't like to spray around the pond. Here's how I control unwanted cattails. A couple times a year I mix up roundup in an old jar and use one of those disposable foam paintbrushes to paint it on the leaves. Just one swipe on 2 or 3 leaves of each plant always kills them. A lot less chemical and it avoids overspray going into the pond. Too time consuming for a large patch but an easy way to kill small patches that show up every year.
Back in the day when Roundup was very expensive, this was the method first used in crops that were not Roundup resistant technology. Called the rope wick bars or various variations. A PVC tube was filled with RUP with wicking ropes extending along the tube. The ropes would wick the roundup up, then by driving over weeds taller than the crop (Johnfongrass mostly) the Roundup would be "wiped" onto the plant. Being systemic, only a small portion of the plant needs contact as long as the solution is strong.
Pictures probably say it better than words.
weed wiper pics hand versions My point is, the way you are doing it with the foam paint brush is actually a very effective way of using the chemicla. 100% on target.
