I have seen some articles that say that it is tough to treat with herbicides. Therefore, they recommend biologic controls - such as grass carp.
The link below recommends GC. It also lists Diquat or Fluridone (Sonar) as the recommended herbicides. (The Sonar would be really expensive for a pond as large as yours!)
I normally like the TAMU stuff and use their info where it applies in Kansas. However, their link to spikerush control say there are no good biologic controls. They also say there are four different species in Texas, so I included that link.
I can't remember if you have crayfish in your pond. The aquatic portion of the of the spikerush seems like something they would really like. However, I can't find anybody saying that crayfish will prune it back?
I also found you an old PB thread. No one had any great biologic answers in that thread. There were some mixed results on the Diquat.
Hopefully you can get an expert or another Pond Bosser from your area that has beaten it to chime in!
Well it seems there is a lot of confusion about this weed. Mine is the totally underwater variety that Kelly Duffie pictured. Don’t know if grass carp will eat it or not. Even Todd Overton doesn’t seem to know.
