I know for a fact they use 2 formula's. A cold water formula and warm water formula. They react differently when sprayed but I thought they were formulated to kill on contact. Not when dispersed. I think it's a combination of several things already mentioned. The contractors over sprayed since they get paid I'm sure by product amount. So collateral damage of pads, haygrass were most affected. The intense flooding another factor. They've been spraying north end of rayburn for 20+ years. They are years with the right level and clarity the grass grows like crazy in the same area that are heavily sprayed. Now I'm not saying there's zero impact, but the product used has shown to have no effect on subsurface vegetation. After these "floods" how much does the silting in of these aging lakes affect the grass being able to reestablish? These lakes aren't young and I know they are silted in like crazy in many of these creeks. It doesn't explain the main lake grass or lack thereof, but something has happened for sure.

Most of the submerged aquatic plants bass fishermen talk about hydrilla, coontail, milfoil, etc and call "grass" are actually no such thing. They are actually broadleaf weeds that can absolutely be affected by runoff of a broadleaf weed killer. With that said, I think that it's pretty rare in this day and age. Most of the highly water soluable formulations have been pulled off the market. It still happens I'm sure in the major row crop growing areas but it's nothing like it was a decade ago. Nutrient runoff is probably a bigger issue these days than actual herbicide.

As to Kens point I'm not 100% sure what herbicide he is talking about. I know around that time period a chemical known as Atrazine was getting lots of publicity. It is a preemergent Herbicide that was widely used in row crops as well as almost every weed and feed lawn fertilizer at that time. Lots of water supply managers were finding traces of it in drinking water. Ag took alot of the blame and some was justified. However they ended up finding that a large portion of the runoff from this particular chemical was actually coming from urban areas where people were horribly over applying their lawns. I have no doubt that this chemical could have had some pretty substantial impacts on aquatic vegetation. Now days most row crop farmers don't use products like Atrazine as much because of the roundup ready technology. I believe the water supply corporations in Texas still test for it so I'm sure that data that could be had if desired.

I personally think that most bass fishermen horribly underestimate the effects of water level on these aquatic plants. Rayburn is a good example. The fact that the super high water levels wiped out a big chunk of the main lake grass is the most predictable thing ever. You put 12ft of water on top of these plants and its going to kill them in most cases. We have seen it time after time on that lake. I'm not saying water level is the only thing going on but it's a big part of the puzzle that often gets overlooked on here.

I apply all kinds of herbicides as a landscape maintenance contractor and we are lucky to get 90 days of control (glysophate, dichloro-phenoxyacetic acid, halosulfuron-methyl, etc.). I can't imagine any herbicide applied per the label that would knock out an entire lake. Weather patterns contribute heavily to issues with weeds and my guess is that the high water killed more grass than any herbicide application did.

You are correct there is little to no farming. But there is lots of herbicide spayed on pastures and yards every year.

I am going to spin this a different way, we have all pointed at different reasons why we have lost the grass. I would like to hear or see some ways to get it back. How do we reverse the loss of the grass. Tennessee Bay used to be covered in it for many years I haven't seen any grass there in at least a decade. How do we get it back?