Water warming up, and Geese pooping seeds into the pond. EWM is a PITA to control, I fluridoned the pond 2 years ago and it did the trick, but I came home one day to 40 of the buggers sitting on the pond. There is a lake <2 miles away that was loaded with it, I think they brought it from there. The lake is 365 acres and last year they fluridoned the whole thing. I can't imagine what that cost!