Years ago I remember reading ponders using Roundup in stead of Rodeo I think it was to take out cattails. Then later years later I had two ponder/farmer friends that used Roundup on their cattails since they had plenty of Roundup in barrels. To kill weeds and grass in my drive I use a very cheap "ELIMINATOR weed & grass killer" $8 makes 10 gallons. A month ago I did a small test spray on cattails and spatterdock and both died. Next year I will probably do a little spot spraying from my boat. Any thoughts on this?