Ensuring your crop protection products successfully hit their intended target can save you money, decrease your liability risk and improve relationships with neighbors. Properly applying rice herbicides also increases weed control efficacy.
To make the most of your weed control applications, Jason Bond, Mississippi State University weed scientist, shares his best management practices for greatly reducing the potential for off-target movement.
“Placing rice in blocks is an easy thing to do if weather conditions and farm location allow. If that is not possible, at least have a plan to create a buffer between your rice and your soybean, corn or other crops,” Bond says. “Rice growers in states such as Arkansas do a good job of planting in large blocks, but they have a lot more rice acres. In Mississippi, our rice is more checkerboarded into the landscape.”
Develop your weed control plan before you begin planting, no matter the crop. Weather and commodity prices can alter planting plans. Knowing which herbicides are safe for which crops is crucial to minimizing potential off-target movement.
Being prepared with a weed control plan will also ensure you start the growing season with a clean rice field.
“At planting, preemergence treatments are the foundation of effective rice weed control,” Bond says. “A good solid preemergence program is critical to season-long weed control. About 95% of Mississippi’s rice crop gets Command herbicide applied at planting.”
“Preemergence burndown treatments have been known to move to early planted rice,” Bond says. “In some years, we’ve had significant rice acres replanted due to glyphosate drift. The years we’ve had the worst problems have been the years weather conditions have been bad.”
Postemergence herbicides sprayed on March-planted rice could potentially affect April-planted soybeans.
“Some herbicides are safe to broadleaf crops. For example, corn is not susceptible to Grasp SC herbicide,” Bond says.
“Avoiding off-target movement is often about making good applications, which can be beyond the grower’s control,” Bond says. He defines a good application as one made within the proper wind speed parameters with favorable wind direction and ample water volume.
Whether applying herbicides by air or ground, the Mississippi Bureau of Plant Industry’s county-specific regulations for glyphosate applications can be used as a best practices guideline.
Bond recommends applying some of those same concepts with rice herbicides. One prime example of a best practice is employing downwind buffers to prevent rice herbicides from reaching susceptible crops.
“Be cognizant of wind speed and direction and make a conscientious application,” he says.
Postemergence weed control timing may change if your planting date changes due to weather; you are forced to replant; or adverse weather conditions make timely herbicide application impossible.
“Sometimes weather prevents us from making a timely application, and you go from spraying one-leaf barnyardgrass to three-leaf barnyardgrass or three-tiller barnyardgrass,” Bond says. “Often, we are rushing to get herbicides out and the weather simply doesn’t cooperate. Having a backup plan will enable you to control whatever weed species are present at the time of your herbicide application.”
A change in herbicide application timing can also change the weed species being targeted for control.
For example, Bond says, if rice is planted in March and temperatures stay cool, Palmer amaranth is less likely to come up because it needs warm weather to germinate. However, with late-planted rice, Palmer amaranth often emerges with the rice, necessitating immediate control.
“Planting date can really change your postemergence weed control plan,” he says. “I’m a staunch advocate for including a residual herbicide at planting."
"Residual herbicides buy you time and provide insurance for your emerging crop.” — Jason Bond
In addition to wind speed and direction recommendations, herbicide label requirements specify the water volume that should be used when applying.
“Higher application volume creates a larger droplet size, which is less prone to moving off-target,” Bond says. “You can’t spray 7 gallons per acre and get a coarse droplet. You need increased water volume to get those larger droplets.”
Bond also recommends choosing spray nozzles that produce a medium-size droplet. “You don’t want a super-fine droplet that is susceptible to moving off-target,” he says.
Grasp® SC is not registered for sale or use in all states. Contact your state pesticide regulatory agency to determine if a product is registered for sale or use in your state. Always read and follow label directions.