Weed scientist studies new herbicide for potential use

LSU AgCenter weed scientist Connor Webster. Photo by Olivia McClure

A herbicide offering the first new mode of action in more than three decades is being studied at LSU AgCenter research stations.

The herbicide’s active ingredient is tetflupyrolimet and is being developed by FMC Corporation. It is a pre-emergence grass residual herbicide that causes little to no injury to rice. Studies are underway to determine how it could fit into rice production in Louisiana.

“This project was a big portion of my research program this year,” said LSU AgCenter weed scientist Connor Webster.

He is running trials at the H. Rouse Caffey Rice Research Station in Crowley and the Northeast Research Station in St. Joseph looking at how the herbicide performs in various soil types and water management systems, including delayed flood, water-seeded pinpoint flood and row rice.

“Studies evaluated optimal rate ranges across soil types, how tetflupyrolimet fits into complete herbicide programs, early season water-seeded application timings, optimal pre-emergence and delayed pre-emergence herbicide mixtures, and applying tetflupyrolimet impregnated on basic fertilizer at planting,” he said.

Other projects include:

  • Provisia tolerance. In collaboration with rice breeder Adam Famoso, Webster has conducted studies to determine herbicide tolerance of rice lines to be used as part of the Provisia system. “The results from these trials will greatly assist in deciding which advanced lines will be commercialized,” Webster said.
  • Overcast weather. An ongoing study is examining how cloudy skies influence the likelihood of herbicide injury in Provisia rice, which was a problem in 2021 and 2023. Earlier this year, Webster used shade cloths to simulate overcast conditions in rice plots. In some, he set up the shade cloths seven days before a Provisia herbicide application; in others, he introduced shade seven days after application. A third group of plots was shaded continuously. He plans to repeat the study twice in the next year to gather more data.
  • Imazethapyr carryover. This issue is a growing concern for those who have planted ACCase-resistant and conventional rice. “Many of the issues that have been experienced are due to the anaerobic conditions during crawfish production that are preventing the breakdown of imazethapyr,” Webster said. “These studies will be refined and repeated over the coming years.”
  • Fimbristylis. Webster is evaluating pre-emergence and post-emergence herbicide options for Fimbristylis, a genus of sedges that is increasingly a problem in rice fields. He’s also studying how the size of the weeds affects control.
  • Spray drones. Webster wants to study the use of drones for weedy rice cleanup in places such as field escapes and corners and around power lines.
11/21/2023 9:56:23 PM
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