Weed scientists with the LSU AgCenter are focusing on a pair of herbicides as promising products to control broadleaf weeds and sedge in rice fields.
AgCenter research associate Connor Webster said the two products, Loyant and Gambit, are known for their broad-spectrum weed control characteristics.
They are being put to the test with application timing trials. Researchers are exploring the herbicides’ efficacies when they are applied before the seeding flood, after the flood directly on the seed and on the one-leaf pegging rice timing.
“Putting out the herbicides directly on germinating seed on the ground in water-seeded rice tends to be pretty injurious,” he said. “Less injury is observed when the rice begins to root and put out a true leaf at the time of application.”
Different application methods are also being tested with the two herbicides. Webster said surface coating Loyant on urea while the fields are flooded have produced some positive results in controlling ducksalad emergence.
“When we drop it in the water, we’re getting a pretty lengthy residual. That was unexpected,” Webster said.
While Loyant and Gambit both have their own stout lists of weed species control, combining the two is showing promising results in field trials.
“The weeds that Gambit seems to be weaker on, Loyant seems to be strong on and vice versa,” Webster said. “They each pick up what the other one misses.”
Gambit is also being studied when applied in a mixture with Stam for control of alligatorweed and several other broadleaf weed species.
Webster and his colleagues are also looking into weed populations in furrow-irrigated rice. Growing rice in upland conditions introduces johnsongrass and pigweed, which are not usually seen in traditional flooded fields.
“We’re seeing more weed pressure because we don’t have the flood on the field to provide cultural control of weed species,” Webster said. “We are seeing a different spectrum without the flood present. We’re seeing more traditional row crop species.”
He said there are several programs in the works to provide weed control in furrow-irrigated rice, but he recommends residual herbicide products like Facet, Gambit or Sharpen with a late post-emergence application.
“People who are applying a late post-emergence are throwing in Command or Prowl to give some residual control because you don’t have the flood to lock in weed control,” he said.
Another new tool in weed eradication that plant scientists are exploring is RiceTec’s Max-Ace rice — a herbicide-tolerant inbred line that can be paired with Adama’s HighCard herbicide to ward off red rice and other grassy weeds. RiceTec released a limited supply of the seed that Webster said differs from the Provisia system that uses the same herbicide, quizalofop.
“It’s the same herbicide, but it has a safener to protect the rice from injury a little bit more,” Webster said, comparing the Max-Ace and Provisia systems. “Max-Ace seems to not have the same tolerances as the Provisia system does.”
In other studies, researchers are revisiting RiceStar, a post-emergent herbicide used to combat grass weeds following Gowan’s purchase of the label from Bayer. The AgCenter is looking at this product with mixtures of residual herbicides.
Webster said the AgCenter is also studying two yet-to-be-released residual experimental herbicides that may soon be added to a grower’s arsenal.