Fall-Applied Herbicides Key to Battling Glyphosate-resistant Ryegrass in Mississippi Rice
STONEVILLE, MS – Mississippi rice producers facing the growing challenge of glyphosate-resistant Italian ryegrass are finding success with fall-applied residual herbicides, according to recent research from Mississippi State University. A study published in Weed Technology demonstrates the critical role of these pre-plant applications in establishing healthy rice stands and maximizing yields.
Glyphosate-resistant Italian ryegrass has become a significant threat to rice production, necessitating timely and effective weed control strategies.Jason Bond, a researcher involved in the study, explains that fall or early-spring herbicide applications are crucial for reducing undesirable vegetation before seeding.
The research, comprised of a Herbicide mixture Study and a Sequential Herbicide Application Study, evaluated various herbicide combinations and application timings. Results showed that dimethenamid-P (Outlook®), pyroxasulfone (Zidua®), and S-metolachlor (Dual Magnum®) each provided over 94% control of the resistant ryegrass 21 days after treatment. While adding flumioxazin (Valor® EZ) didn’t improve long-term control, the study confirmed the necessity of a fall-applied residual herbicide.
“In the absence of a fall-applied residual herbicide, S-metolachlor (Dual Magnum®) can reduce efficacy of clethodim (Select Max®) targeting GR Italian ryegrass,” Bond stated. Furthermore, adding a residual herbicide to a sequential clethodim (Select Max®) application offered little additional benefit.
The study indicated fall-applied dimethenamid-P (Outlook®) generally outperformed fall-applied acetochlor (Warrant®), except when acetochlor was followed by a sequential application of clethodim (Select Max®) plus S-metolachlor (Dual Magnum).
The full research article, “Glyphosate-resistant Italian ryegrass (Lolium perenne ssp. multiflorum) control in preemergence and postemergence programs containing mixtures of residual herbicides,” is available in Weed Technology, a journal published by the Weed Science Society of America (WSSA) and Cambridge University Press.
