That was easy enough, found a jug in shed its called (Shore-Klear) aquatic herbicide. For use on emerged aquatic weeds and brush. I was told by person who turned me on to it to mix 2oz per gal on or very near Labor Day and that worked for me. Just sprayed it on upper green area of cattails wetting them well with a pump-up sprayer just like you use round-up/weed killer. It took 2 years to fully eradicate, a few came back after first year treatment and needed gone over again and no more came back after that. Hope this is helpful for your ponds good luck.