I'm fighting the coontail fight now. It's never too late, however the best time to nail it with herbicides is Spring emergent. Now you have to increase dosage and worry about dead material taking up all the O2. Sometimes the live stuff does that anyway as the pond I am working had a bad die off of LMB. But I am looking at 80%+.
My customer says no to herbicides so I am hand pulling, putting in hybrid carp and mowing with the Lake Mower and raking with the Lake Rake. I prefer to get that material out and let the carp start to get on top of it. Worst infestation I have seen, top to bottom, a couple of free holes in the entire pond. Gone over 10 years no treatment. When I am at low water in the fall I'm hitting it hard mechanically.
What Coontail and it's buddy Eurasian Milfoil do if left unchecked is crowd out evey other species. Then when they go through thier die off cycle they cause internal nutrient loading. Especially Nitrogen and Phosphorous. That then feeds the problem even more and gets algae everywhere too. Pretty soon O2 get sucked up and fish start floating. Even if you herbicide it that boimass dies, sinks and releases the nutrients. And it is almost impossible to totally eradicate it. The coontail free floats, has no roots and will make very dense mats on the surface. Milfoil will also mat up, and both can propagate by fragmentation. Good luck, but I'd look at combined control methods, not just herbicide alone.
