The rice production season is underway. As the rice crop starts to surface, so will unsightly weeds, which threaten yield and the harvest growers look forward to every year. Dow AgroSciences provides some reminders and insight for rice growers and their advisors.

Weeds deprive rice crops of vital moisture, sunlight and nutrients. If left to grow too large, weeds such as barnyardgrass can significantly reduce yields, says Larry Walton, field scientist, Dow AgroSciences. 

To battle emerged weeds, rice growers benefit from a pre-flood and post-flood weed control plan. This is an important part of a weed management program and protects their crop and yield potential against weed threats.

Control postemergence weeds pre-flood to protect yield.

Growers can take steps to minimize weed competition during the early stages of a crop’s growth cycle.

Most grass weeds are highly competitive early in the growing season and should be controlled shortly after they emerge, according to a study from the University of Arkansas. Barnyardgrass, for example, grows faster and develops more biomass than rice at this time, which gives barnyardgrass a competitive advantage.1 When competing with rice plants, this grass species can reduce the number of tillers, panicles and seeds per panicle on a rice plant.2

“Barnyardgrass has become increasingly difficult to control over the years and is one of the greatest weed-control challenges growers face each season,” Walton said. “Early control of barnyardgrass is essential to ensure the developing rice crop is not competing for the moisture and nutrients it needs.”

Stay vigilant and address weeds such as barnyardgrass pre-flood before they get too large and start to affect yield potential, he says.

“It is critical to use herbicides with multiple modes of action to control weeds and manage herbicide resistance,” Walton said.

.Watch for weed escapes post-flood.

Continue to scout fields throughout the entire season; weeds missed in a pre-flood herbicide application can reduce yield post-flood if they are not effectively managed.

Aquatic species in particular thrive post-flood. Aquatic species generally are found in thin stands of rice and water-seeded fields. Establish a solid rice stand to reduce the potential number of aquatic weeds, as well as the potential for diminished yield caused by direct competition for nutrients, sunlight and moisture post-flood.

“A post-flood weed control program combats weed pressure and keeps the crop strong and healthy through harvest,” Walton says. “Pay close attention to post-flood application timing, as it is important to fill in coverage gaps and control weed escapes.”

Flexibility in timing and multiple modes of action for wide spectrum weed control is important with a post-flood herbicide application.

Dow AgroSciences’ rice herbicide product line includes RebelEX for postemergence grass and broadleaf weed control pre-flood. For post-flood application, Grasp Xtra herbicide or Clincher SF herbicide can be applied up to 60 days pre-harvest.

More information on postemergence weed control solutions are available at  DowRiceherbicides.com.

1Scott, B., J. Norsworthy, T. Barber, and J. Hardke. Rice Weed Control. University of Arkansas. http://www.uaex.edu/publications/pdf/mp192/chapter-7.pdf

2Tindall, K., M. Stout, B. Williams, B. Castro, and E. Webster. 2004. Integrating Insect and Weed Management in Rice. Lousiana State University. http://www.lsuagcenter.com/en/communications/publications/agmag/Archive/2004/Winter/Integrating+Insect+and+Weed+Management+in+Rice.htm