Weed Control Options in Light of Herbicide Shortages
By Larry Steckel, University of Tennessee Extension weed specialist
Judging by calls, there is a good deal of frustration with the lack of Caparol, Cotoran and Diuron. A lot of folks are scrambling, trying to come up with a Plan B or even a Plan C as cotton planters roll.
It is clear that some product managers at a few chemical companies woefully underestimated what demand would be this year for those herbicides. Though many are aggravated, I tend to cut some slack to folks who forecast demand for products, as I used to do that for Pioneer on seed. It is clearly more an art than a science.
With an overall lack of the PSII inhibitors, it leaves only Brake FX, Brake F16, Dual Magnum or Warrant. There are down sides to any of those four choices:
- The Brake products are too costly for many folks. This is unfortunate, as these products will provide good pigweed control and are the safest to the cotton crop of the available options.
- Dual Magnum can also provide good pigweed control, but some are worried about crop safety.
- There are crop injury concerns with Warrant as well. Moreover, Warrant needs more rainfall than Dual Magnum to get activated. This difference results in Warrant often providing more inconsistent weed control than Dual Magnum.
So, we are trying to make lemonade out of lemons. Barring the Brake products, the best option would be to use a low rate of Dual Magnum (8 to 12 oz/A). This should be enough to get a couple weeks of residual Palmer amaranth control, while mitigating cotton injury with the lower rate.
If you choose Warrant herbicide, go with 24 oz/A to help mitigate injury, then follow up these applications with an early POST application of 16 to 20 oz/A of Dual Magnum.
Another option early POST would be Outlook. However, supply is short on it as well, and I have had several reports that some growers cannot access the herbicide. The rate of Outlook POST in cotton is 12.8 oz/A (1 Gal/100).
I have also heard that some growers, due to the lack of traditional PRE herbicides, plan now to just use Engenia or XtendiMax as their sole PRE product, then spray one of those products again with glyphosate POST and call their weed control over.
Please do not do that. As I mentioned in a previous blog, there are some questions on how effective dicamba will be on some of our PPO-resistant Palmer amaranth. If all we spray is dicamba and glyphosate this spring, we could be setting up for some major resistance issues in 2018.