Knobber,
I can't remember - what fish are currently in the pond?
If you have undesirable plants that are going to flourish under the existing conditions, then the best time to address the problem is yesterday!
Such plants are only going to drop more seeds, spread more runners, establish better root systems, etc. in your pond.
I would accelerate your plan to identify which plants are growing in that invasive strip. Once you identify most of them, I would then start a new thread in the "Controlling unwanted plants" sub-forum.
There are several pond management experts that typically reply in those threads. They can tell you exactly the right herbicide to target your plants. Specific targeting is the most important thing IMO for wiping out invasive plants.
If you have plenty of water available for your pond, then you could even drain it 1-2 feet so those plants are completely exposed. Then treat heavy with your herbicide while getting very little directly into the pond water. Wait a few days for the herbicide that landed on soil to degrade, and then re-flood your pond.
(That should preserve your existing fish. However, you should probably list all of the existing aquatic life in your pond when you open your new thread.)
