If you are starting to win the duckweed battle, could you do most of the pond this year in a set of waders?

I would NOT want to wear a backpack sprayer while wading. However, if you put a small electric rig on a little floating barge that you towed behind you, then you should be safe to spray.

(That might be more work than loading up the canoe, so just spitballing other options for you!)