Controlling cattails

Question

I am going to spray the cattails with RODEO. Do I spray the entire plant or do I spray at the water line to kill the plant?

Answer 1

Cattails are a perennial with a rhizome. Spraying anytime may kill the foliage, but not the plant. The greatest success comes in spraying glyphosate in the fall after the plant has flowered and as the plant begins to strengthen its root system for overwintering.
Use an aquatic labeled glyphosate.

https://www.gardeningknowhow.com/ornamental/water-plants/cattails/controlling-cattails.htm