Mush,
I have a two acre pond that the Bushy Pond weed also went crazy. It started last year and was the middle of the summer so I bought a rake to help control it until spring. That's a lot of futile work. You just can't stay caught up with this stuff.
My pond has a lot of runoff so I pumped the pond down about a foot hoping that if (when) we got some rain it would not all flow out. I bought 2 gallons of it at a cost of $1.000. a gallon as recommended. The WIPEOUT was able to stay in the water for a little over 30 days before the pond filled up and started to flow out the spillway. Like you we have had an over abundance of rain this year. Just my luck! All the Bushy Pond Weed did die off and the pond became very stained looking but once again fishable.
Unfortunately three weeks ago I am seeing the weed reappear along the banks. It worked but evidently it did not kill the roots. The label says that the weed must stay in contact for 60-90 days. Sorry but I just can't afford to send that kind of money again. I am at a loss. Hope this helps you.