I got a call this week to go to a pond for weed ID and control. I ended up seeing brittle naiad submersed, filamentous algae, and water primrose floating. Water temperatures are nearing 70 degrees F and the best cool water treatment is diquat:cutrine plus at 1:1. Use up to two gallons of each chemical per acre based on water depth. In water less than 2 feet deep use one gallon of each.
You need to apply directly over the weed bed using 25 to 100 gallons of dilution water per acre. Stock triploid grass carp to continue control at the rate of 10 per infested acre.
The Cutrine is copper-based and is for algae, and the diquat is for the submersed/floating weeds. It is important to get pond weeds identified because diquat does not work on certain weeds, and cutrine is not perfect on all algae.