Plan Ahead for Success

Plan Ahead for Success

Jarrod Hardke, University of Arkansas
Professor/Rice Extension
University of Arkansas System Division of Agriculture

Each year those reporting the most successful weed control programs continue to be those who focus on overlapping residuals. That, plus starting clean and putting the right chemistry / technology where it has the best chance for success.

Burndown herbicide applications help us to start the season clean, but plant-back intervals must be carefully observed. Some fields received fall applications of Dual and should not be planted to rice this spring (expect a 10% yield reduction and 25% stand reduction). Fall-applied Command can be followed with rice planted in the spring, but season total use limits must be followed. Plant-back intervals for spring burndown applications of 2,4-D, dicamba, Elevore, Select, and Valor (14-30 day plant-back depending on herbicide) should also be used with caution as we approach planting time.

Be careful where you place your herbicide technologies and how you approach your weed control program in them. We have barnyardgrass and weedy rice populations confirmed resistant to Newpath/Preface. There are also weedy rice populations resistant to Provisia/Highcard.

This photo of a rice field heavily infested with barnyardgrass, taken in June 2020, shows the repercussions of not getting a jump on the weed with overlapping residual preemergence treatments.

If you planted a Clearfield or FullPage cultivar last year and sprayed Newpath or Preface, you need to rotate to another crop — you cannot rotate to conventional rice or Provisia/MaxAce due to carryover issues. If you planted a Provisia or MaxAce cultivar last year, you need to rotate to soybean due to concerns with outcrossing and potential loss of this technology.

Plant into a stale seedbed environment, if possible, to maximize our rice stand and to minimize weed emergence from disturbing the soil. Let’s discourage weed emergence in the first place.

Start clean with a good residual program of Command combined with appropriate other herbicides for your farm. Follow that up with an overlapping residual before weeds emerge, which may include Prowl, Bolero, Facet, or more Command in some combination (use multiple modes of action).

The economics of rice production will be tough in 2024, and we don’t want to skimp on our herbicide programs. If we focus on getting residual herbicides applied and activated, that’s the best way to keep our weed control budget under control. Post-emergence herbicide applications can get very expensive very quickly. While we don’t like to see weed escapes, sometimes you have to stop and remember that perfect weed control isn’t necessary to achieve a perfect yield. Good luck in 2024.

Weed Control Strategies for 2024

justin chlapecka
Assistant Research Professor/
Rice Extension Specialist
University of Missouri

As meeting season is finally winding down, many of us are just a few weeks away from putting a drill into the field. As we move into Plant ‘24, a good portion of ground is ready to go after the dry fall season. While planting into a stale seedbed will be a great option in that scenario, we must think more about burndown applications in the absence of spring tillage. Some may have already applied a burndown, but starting clean is absolutely essential to having a clean rice field come August.

My idea has always been to get a good burndown at planting, but you must be sure that what you apply is going to work, as we likely won’t get a second chance if the rice emerges very quickly. Clomazone is an essential application at planting, as a pre-emerge for barnyardgrass and most other grasses that we will contend with during the season. We routinely see the best weed control where pre-emerge products are overlapped at a bare minimum of 21 days apart. In fact, somewhere around the two to two-and-a-half week time frame is ideal for overlapping residuals in a furrow-irrigated rice system.

The best way to kill grass in a rice crop is to never see it above the soil surface. Once we see grass in the field, we are already behind the eight ball. While there are generally fewer resistance issues in Missouri than further south, we do have our fair share of problems where continuous rice has been grown.

If you suspect herbicide resistance is an issue, imazethapyr-tolerant rice is a great tool for barnyardgrass and weedy rice control. In some areas, however, resistance has developed to imazethapyr, but quizalofop-tolerant rice could be another tool in the toolbelt. Yield has lagged since this technology was released, but the newer cultivars have shown tremendous improvement and there are more in the pipeline.

In related news, we will greatly miss having Jim Heiser as our weed scientist in the Bootheel. As we try to fill that gap, if you have any rice questions now or in-season you can contact us via e-mail at As always, eat MO rice!

New Herbicides Add Tools to Weed Management in 2024

Whitney Brim-Deforest
Cooperative Extension
Rice Advisor
University of California, Davis

This year brings several new chemical tools to California rice. With many herbicide-resistant species as well as emerging problematic weed species, the new chemistries are a welcome tool for managing resistance and preventing the selection of resistant biotypes.

Last year, we had use of Loyant CA Rinskor active (florpyrauxifen-benzyl) for the full season (registered late in 2022). Loyant, which is an auxin mimic, is applied as a foliar product. It gives additional options for early-season control of sedges and broadleaf weeds, and although not strong on watergrasses when applied alone, provides added control when tankmixed with other herbicides for grass control. Based on data collected in 2022-2023, two good tank-mix options for watergrass control are SuperWham/Stam (propanil) and Regiment (bispyribac-sodium). It does not control sprangletop.

Bearded sprangletop (left) and Mexican sprangletop

Cliffhanger (benzobicyclon) was just registered in 2024 and is a new formulation of a previously-registered granular product already widely in use in California rice. Since it can be applied as a foliar product, it expands the timing that benzobicyclon can be applied in the flooded system. It can also be applied as a direct-stream application into the water. It is an HPPD-inhibitor, providing a good option for rotation. It controls sprangletop, ricefield bulrush and smallflower umbrella sedge. Additional tank-mix testing will be occurring this season to determine if it might be a good partner in combination with other herbicides for added late-season watergrass control.

The last product recently registered is Zembu (pyraclonil). Zembu is a granular formulation of pyraclonil, applied pre-emergence or at day-of-seeding into a flooded field. It provides control of smallflower umbrella sedge and broadleaf weeds and provides suppression of watergrass. As a PPO-inhibitor, it is a new mode of action for watergrass, as the only other PPO-inhibitor registered in California rice only has activity on sedges. It will provide a great rotational option for growers at the beginning of the season, as well as a great partner product (for added control) with other granular into-the-water products.

As always, the label is the law, so make sure to read and follow the current labels for each of these herbicides (found on the manufacturers website or at the Department of Pesticide Regulation’s website). Also check in locally with your Agricultural Commissioner’s office for training information and any other county-specific requirements.

With these three new options, as well as the currently registered products, rice growers in California should have a great suite of tools available this year, both for resistance management as well as to prevent the selection of future resistance. For help planning a weed management program, please reach out to your local Rice Farm Advisor.

Weed Control Using Water

ronnie levy
Extension Rice Specialist
Louisiana State University

Proper water management is a key component in controlling weeds. Several different water management schemes have evolved in Louisiana, and two major planting systems dictate the basic water-management strategies used by producers.

Historically, a majority of Louisiana’s rice is in Southwest Louisiana and most of this acreage was planted using a water-seeded system prior to the commercialization of Clearfield rice and now Provisia rice. The introduction of herbicide-resistant rice has caused a shift from water-seeded to dry-seeded rice in Southwest Louisiana. The remaining acreage is grown in northeast Louisiana, where dry seeding methods are more common.

In water-seeded rice, the weed spectrum generally changes from a predominantly annual grass problem in drill-seeded rice to more aquatic weed problems. If a water-seeded system is used for several years, it may cause a shift in the weed spectrum from terrestrial to aquatic weeds. The predominant weeds found in this production system are alligatorweed, ducksalad, grassy arrowhead, common arrowhead, creeping burhead, pickerelweed, and roundleaf mudplantain. Two types of water management systems are used by producers: (1) pinpoint flood, and (2) delayed flood.

Water seeding is strongly tied to weed management. Weed seeds have the same requirements for germination as rice — proper temperature, water, and oxygen. By flooding a rice field before temperatures have risen to levels sufficient for germination, two of the requirements for weed development are at least minimized. The cool temperatures at planting reduce germination, and the flooded soil will become saturated. Saturated soils have little dissolved oxygen in them; thereby reducing weed seed germination and emergence.

Using Water Aids in Reducing Weed Populations

In situations where weeds are not controlled with labeled rates of herbicides applied under environmental conditions that are favorable for herbicide activity, these weeds may be resistant.  Changing herbicides with different modes of action may prevent or delay development of resistance in Louisiana.

Rice producers in Louisiana have been fairly successful at keeping resistance problems to a minimum, but with increased weed resistance or without newer control options, the use of water to increase weed control may return.

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