I am hoping that your coontail just kept migrating down your pond slope and now it died off due to lack of sunlight in a full pond because the light had to reach it through several more feet of muddier than usual water.

Do you know your neighbors well enough to ask what chemicals he was actually spraying?

I believe Kansas State has a water testing department. Perhaps they could test for a specific herbicide if you told them which product?

Might take a water sample from your inlet creek on the day they spray, and another sample right after a rainstorm?


P.S. Have you been fishing since losing the coontail? I suspect the artificial structure you have placed will really be acting as a fish attractor/concentrator right now!