I dont think you are supposed to spray white cap. When I use it I mix it with water in a five gal. bucket and then just poured it into the pond. Its not a contact spray. How many oz. did you use in your pond? When I did one of my 1/2 acre ponds to kill watermeal I used 32 oz and within 60 days there wasn't any weeds in the pond anywhere. It says that it could take up to 90 days to work though. Was there still water flowing out of the spillway when you used it? Have you been seeing any resultd from where you sprayed?