<font color=blue>putting a few drops of dish washing liquid in the spray mix for adhesion?</font color=blue>
That's what its for, and Jerry Baker recommends dishsoap for his lawn and garden care mixtures. You could also use something like Bonide's "Turbo-Horticultural Spreader-Sticker" that works to wet the leaf's surface, despite some leaf's ability to shed water (I think cattails would fall into that category). I bought 2 oz at the local garden center for $4. That amount will treat 30 gallons of spray for "Very Hard to Wet Plants", up to 240 gallons of spray for "Moderately Hard to Wet Plants". I use it for my fungicide since it seems to be difficult to get to stick to the leaves, but the bottle says it can "improve performance of insecticides, miticides, fungicides and weed killers".