No-till without paraquat? That may be a possibility. Syngenta announced they will stop producing Gramoxone in June. This will leave only the companies that sell the generic paraquats to fill the demand. Will those companies be willing to take on the lawsuits to continue to sell a low margin herbicide? Maybe. Beyond that, the probability one of those companies in a few years will take the lead on re-registration with the EPA is low. All that would suggest that the time span paraquat is available could be as short as just a few years. If so, we need to have a Plan B to replace this herbicide in Tennessee over the next couple years. This will be the emphasis of some of our research this year.
Finding a good substitute will not be easy, particularly with Palmer amaranth. Liberty would be the most obvious alternative but it has two real drawbacks as a burndown. First, unlike paraquat which works well across most temperatures, Liberty will not work well when temperatures get much below 80 degrees. Second, Liberty resistant Palmer amaranth has been confirmed just across the river in Arkansas and, judging from some greenhouse screening we have done, may have arrived in Tennessee.
Liberty mixed with dicamba or 2,4-D can provide some Palmer amaranth control, but in areas with auxin-herbicide resistant populations control can be inconsistent. It typically takes 2 applications of that tankmix applied 14 days apart to provide something close to good control. Clearly this is not as economical or effective as a single paraquat application but the phrase “any port in a storm” comes to mind.
We will have to explore other more creative options like Liberty tankmixed with metribuzin or diuron. Some of the more promising avenues would be some experimental non-selective herbicides being developed by industry. However, the registration process is very slow and it will be years, if ever, before they are available.
Tillage of course works. However, we moved away from tillage due to Tennessee soils being so susceptible to erosion. I cannot see how farming in many Tennessee fields would be sustainable if we have to go back to the amount of tillage done in the 1980s, where mud slides out of fields closed roads. Hopefully, we will find better alternatives for growers to employ if and when we do lose paraquat. Maybe we won’t have to worry about it but it’s best to try to think ahead and be prepared if at all possible.
