"We have 19 herbicides that we use in rice, and, in nine of those, we have documented resistance by weeds in the rice field,” says Arkansas farmer and researcher Ronnie Helms. “The only two grass herbicides that we don’t have resistance to are Bolero and Prowl.”
This statement alone makes more than a good case for using multiple modes of action (MOA) to attack weed pests. Helms shares his weed control program on his own no-till rice farm.
“In our Clearfield rice, we start off with Roundup and Command, then plant into that,” he says. “Next we put out Newpath and Command or Newpath and Prowl because we have so much sprangletop. On the next application, there is an array of products we can use depending on the weed spectrum. It may be a Newpath, Clearpath combination, which provides some Facet, or Newpath, propanil or Newpath, Rice Beaux – a combination of Bolero and propanil, two more modes of action.
“Depending on the combinations we choose, we sometimes use seven MOAs to control weeds in our Clearfield rice,” he adds. “Given the weed spectrum we have in this aquatic environment, we have to use this approach.
“As for the RiceCo products, that company is taking old chemistries and mixing different modes of action resulting in products like Rice Beaux, RicePro and Duet and creating more viable herbicides given the resistance management awareness that everybody has right now,” he adds.
Helms also uses an array of herbicides with different MOAs in his no-till conventional rice production system.
“A conventional rice weed control program after Roundup and Command may include Regiment, Grasp, Clincher or RiceStar HT or other herbicides tankmixed with Command or Facet, depending upon the weed species and size and the growth stage of the rice,” Helms says.
Marc Cummings, who consults on rice fields in northeast Arkansas and southeast Missouri, says he uses a lot of Duet (Londax and propanil) in his weed control program for the Clearfield rice system.
“It depends on the field, but Duet usually goes in with the second shot of Newpath before the permanent flood, especially fields with a history of nutsedge and black-seeded weeds such as coffeebean, indigo and ducksalad,” Cummings says.
In fields with a lot of grass pressure, the Arkansas consultant says he usually adds RicePro (Super Wham and Facet) or Rice Beaux with the first shot of Newpath.
“Rice Beaux works well in fields with a history of sprangletop and barnyardgrass that has become resistant to some of the stam products,” he says.
On conventional rice, Cummings says most of his farmers put out Command, which he says usually holds over to three and four-leaf rice. Then, at that point, he applies herbicides with different MOAs. By using this preventative approach, Cummings has very few resistant weeds.
“If I had not been using these products with different MOAs, I would probably be seeing a lot more resistance,” he explains. “If you haven’t been using herbicides with different MOAs, and you begin getting resistance in certain weeds, take a look at the herbicides you have used over the years, what the weeds have become resistant to and try to put together another program.”
Cummings notes that behind red rice, barnyardgrass is the No. 1 threat to the rice market today.
“I’m also beginning to see more smartweed resistance,” he adds. “Duet has worked well in keeping that weed down, but, besides using different MOAs, timing also is an important aspect of your herbicide program to help avoid resistance. Get the weeds when they are small. Don’t take chances on letting them get bigger and harder to kill.”
On a final note, Helms emphasizes the importance of being aware of how many rice herbicides are in the market and “the only two herbicides that we have for grasses that we don’t have resistance to are Bolero and Prowl,” he says. “And looking down the road, we can’t grow a rice crop with just those two herbicides. We have to be really smart in managing our weeds.”
Contact Carroll Smith at (901) 767-4020 or email@example.com.