UACES Facebook Arkansas Rice Update 7-30-21
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Arkansas Rice Update 7-30-21

by Jarrod Hardke, Rice Extension Agronomist - July 30, 2021

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Arkansas Rice Update 2021-19

July 30, 2021

Jarrod Hardke, Nick Bateman, Gus Lorenz, Ben Thrash, Tommy Butts, Jason Norsworthy, Tom Barber, and Scott Stiles

“Here I am in this dang bed, and who’s gonna feed them hogs?”



Some Like it Hot

Jarrod Hardke

If you’ve been in the field this week then you’ve been cooking.  More conversations have turned to debating whether it’s better to be out in the morning in the higher humidity and heavy dew or later afternoon when it’s drier but hotter.  Opinions vary, but either way it’s hot.

It does appear that relief is on the way this weekend.  Temperatures are expected to drop below normal beginning Sunday and stay somewhat mild through the week.  As we struggle to stay caught up on irrigation efforts, this will be a welcome relief.  Some rainfall is expected on Sunday but amounts and locations still look up in the air.  May everyone get just what they need!

Difficulty keeping fields flooded and early season weather making herbicide applications difficult are finally showing through in the form of weed escapes.  Grass is beginning to make it out of the canopy in areas that seemed pretty clean throughout much of the year so far.  Often the pressure looks worse than it really is at this point as large tillering grass makes populations looker thicker.  Certainly, there will be lodging concerns in those areas of the field come harvest time.

A major note for this week is that, due to rising numbers of COVID cases, the decision has been made to CANCEL the Rice Field Day at Stuttgart on Aug. 6 and the Rice College at Pine Tree on Aug. 12.  If you paid a registration fee for Rice College, it will be refunded.

We’re disappointed not to have these events, but the safety of attendees comes first.  In their place, we plan to video the content from these events and make them available online at a later date.  It’s not a perfect substitute for in-person, in-the-field events, but we’ll try to make them as close as we can.

Fig. 1.  NOAA 7-day Precipitation Forecast.

NOAA 7 day precipitation forecast


Insects:  Good News and Bad News

Nick Bateman, Gus Lorenz, and Ben Thrash

Fall Armyworms

The good news is we were successful in getting a crisis exemption for the Intrepid 2F for use in rice to control armyworms.  The specific exemption is still under review at EPA and it may be another month before they make a final decision, but as of July 28th we are legal to spray in Arkansas.  If something changes, we will let everyone know immediately.  We have observed great efficacy with 4 oz.  Some highlights for the exemption are listed below.

Intrepid 2F Crisis Exemption Highlights:

Some of the calls we are getting on armyworms currently are for headed rice.  Once rice is headed we are still concerned about defoliation, especially if it exceeds 20%.  This isn’t common to see in headed rice, however it can happen.  One thing to keep an eye out for is if armyworms are moving on to the panicle.  We have documented them feeding on blooms and in some cases seed, which can lead to a reduction in yield.  If this is observed, treatment may be warranted.  Keep in mind that armyworms on panicles are very exposed, and we would expect to do a better job with lambda-cyhalothrin (Warrior II, Lambda-Cy, etc.) than when armyworms are down in the canopy.

Rice Stink Bugs

With all of the armyworm issues going on in rice, we haven’t talked much about rice stink bugs.  In some places in the state, folks are on their second and third applications.  Most of these situations are because they are the only headed rice around and keep getting reinfested.  We are getting questions in a lot of these cases on whether or not we should swap to Tenchu and stop spraying lambda.  We have made several collections from these locations over the past week and are not seeing issues with lambda yet.  A sign of control failure is having nymphs following an application, if it is just adults, then it is most likely a reinfestation.  Please contact us if you feel you are not getting adequate control with lambda so we can conduct some bioassays.

Acephate Use in Rice – The Bad News

The last thing we want to cover is the use of acephate in rice.  This is an illegal application and runs the risk of jeopardizing the rice industry as a whole.  We have gotten a few questions about using acephate for both fall armyworm and rice stink bug control.  Once again, this is highly off label.  Acephate is easily detected in grain even at drift rates.  Our work has shown that a direct application or drift rates lead to levels that are high enough to be rejected at foreign ports.  Please do not use acephate in rice.


Pennsylvania Smartweed Confirmed ALS-Inhibitor-Resistant in Arkansas

Tommy Butts, Jason Norsworthy, and Tom Barber

Smartweed species (Persicaria spp.) have been reported as important weeds to manage in Midsouth rice acres (Norsworthy et al., 2013).  Acetolactate synthase (ALS)-inhibiting herbicides have become the go-to options for successfully managing these species postemergence in rice (Barber et al., 2021).  The heavy reliance on ALS-inhibitor chemistries for smartweed control in rice resulted in a population of Pennsylvania smartweed [Persicaria pensylvanica (L.) M. Gomez] from southeast Missouri being previously confirmed ALS-inhibitor-resistant (Varanasi et al., 2018).  No such resistance has been confirmed in Arkansas; however, recent suspicions and reports of suspected ALS-inhibitor-resistant smartweed have begun to emerge.  As a result, the objective of this research was to perform a dose response experiment on a suspected ALS-inhibitor-resistant (Jackson County, AR) and susceptible (Lonoke County, AR) Pennsylvania smartweed population.

Greenhouse dose response experiments were conducted in the spring and summer of 2021 at the Lonoke Extension Center located near Lonoke, AR to assess if ALS-inhibitor-resistant Pennsylvania smartweed was present within the state.  Two Pennsylvania smartweed populations (one suspected resistant population from Jackson County, AR, and one susceptible population from Lonoke County, AR) were subjected to various rates (0.25x, 0.5x, 1x, 2x, 4x, and 8x of a label rate) of two ALS-inhibiting herbicides [bispyribac-sodium (Regiment) and halosulfuron + prosulfuron (Gambit)].  The 1x label rates used for Regiment and Gambit were 0.5 and 2 oz/ac, respectively, and appropriate adjuvants were included in each treatment as indicated by the herbicide labels.  Treatments were sprayed using a single-nozzle research track sprayer (DeVries Manufacturing) calibrated to deliver 10 gallons/ac using an XR110015 EVS nozzle.  A minimum of 3 replications (plants) were evaluated per run and 2 separate experimental runs were conducted. At 28 days after treatment, plants were harvested and weighed for aboveground biomass measurements.  Biomass data were standardized compared to the nontreated control and analyzed using the dose response package (drc) in R v4.0.3 (Ritz et al., 2015).  Three parameter log-logistic regression curves were fit to the data with maximum values fixed at 100.

Results of the greenhouse dose response study indicate the Jackson County, AR Pennsylvania smartweed population to be between 5 and 10-fold resistant based on the estimated dose to reduce biomass by 50% (ED50) and between 38 and 60-fold resistant to reduce biomass by 90% (ED90) for both Gambit and Regiment (Table 1).  Dose response curve figures for both Gambit (Fig. 1) and Regiment (Fig. 2) illustrate the reduced control observed with each ALS-inhibiting herbicide on the Jackson County population compared to the Lonoke County susceptible.  This is also demonstrated in the images taken from the greenhouse experiment for the resistant (Fig. 3) and susceptible (Fig. 4) populations at 28 days following the application.  To successfully control the Jackson County Pennsylvania smartweed population (reduce biomass 90%), it would require a 34.6 and 24.4 oz/ac rate of Gambit and Regiment, respectively, which is approximately 17 and 48 times more than labeled rates of each herbicide, respectively (Table 1).

This research confirms the existence of ALS-inhibitor-resistant Pennsylvania smartweed within Arkansas. Additionally, as the Jackson County population was confirmed resistant to both Regiment and Gambit, this demonstrates the resistance is present across different chemical families within the ALS-inhibitor site-of-action.  This can be extremely problematic for rice producers within the state as it effectively removes an entire site-of-action available for the control of Pennsylvania smartweed.  Remaining options would include Basagran at 2 pt/ac, propanil at 4 qt/ac, and Aim at 1.25 fl oz/ac.  However, as all of these are contact herbicides, adequate coverage and applying when smartweed is small (~4 inches in height) is a must for successful control.  Sequential applications of these herbicides will also often be required for complete control.

If you have smartweed or other problematic weed concerns in your field crops, please don’t hesitate to get a hold of us. Good luck out there!

Fig. 1.  Dose response curves for a suspected resistant and susceptible Pennsylvania smartweed population following an application of Gambit (halosulfuron + prosulfuron) herbicide.  The 1x label rate of Gambit was 2 oz/ac.

Dose response curves for Gambit on smartweed


Fig. 2.  Dose response curves for a suspected resistant and susceptible Pennsylvania smartweed population following an application of Regiment (bispyribac-sodium) herbicide.  The 1x label rate of Regiment was 0.5 oz/ac.

Dose response curves for Regiment on smartweed


Fig. 3.  Dose response of suspected ALS-inhibitor resistant smartweed from Jackson County, AR 28 days after treatment of bispyribac-sodium (Regiment) and halosulfuron + prosulfuron (Gambit).  The 1x rate for Regiment and Gambit was 0.5 and 2 oz/ac, respectively.

Dose response suspected ALS resistant smartweed


Fig. 4.  Dose response of susceptible smartweed from Lonoke County, AR 28 days after treatment of bispyribac-sodium (Regiment) and halosulfuron + prosulfuron (Gambit).  The 1x rate for Regiment and Gambit was 0.5 and 2 oz/ac, respectively.

Dose response ALS susceptible smartweed


Table 1.  Estimated herbicide doses required to achieve 50% (ED50) and 90% (ED90) Pennsylvania smartweed biomass reduction.

Estimated herbicide dose to acheive 50 and 90 pct smartweed biomass reduction


Literature Cited:

Barber, L.T., Butts, T.R., Boyd, J.W., Cunningham, K., Selden, G., Norsworthy, J.K., Burgos, N.R., Bertucci, M., 2021. MP44: Recommended chemicals for weed and brush control. University of Arkansas System Division of Agriculture, Cooperative Extension Service, Little Rock, AR.

Norsworthy, J.K., Bond, J., Scott, R.C., 2013. Weed management practices and needs in Arkansas and Mississippi rice. Weed Technology 27, 623–630.

Ritz, C., Baty, F., Streibig, J.C., Gerhard, D., 2015. Dose-response analysis using R. PLoS One 10, e0146021.

Varanasi, V.K., Norsworthy, J.K., Brabham, C., Scott, R.C., 2018. Characterization of acetolactate synthase (ALS)-inhibitor resistance in Pennsylvania smartweed (Persicaria pensylvanica). Weed Sci 66, 710–714.


Rice Market Update

Scott Stiles

The big news this week came on Thursday with the announcement of U.S. rice sales to Iraq.  This pushed nearby futures up to $13.85 at one point in Thursday’s trading.  September rice futures followed the other CBOT grains lower in early trading Friday.  However, the contract remains in an up-trending channel that’s been in place since July 12th.

CME September ’21 Rice Futures

CME Sept 2021 Rice Futures

Thursday’s Export Sales report included activity for the week ending July 22.  As the 20/21 marketing year winds down, sales were low volume which is not unusual.  Long-grain rough rice sales were 6,500 tons (all to Mexico) and long-grain milled sales dipped to a marketing year low of 1,429 tons.

There’s one (1) week and 2 days of export sales left to report in the old crop marketing year.  At this point long-grain rough rice sales are up 27% from last year.  Sales of 120,150 tons to Brazil have helped.  But the largest year-on-year increase in rough rice business has been to Venezuela with sales up 490%.  Sales to Mexico and Nicaragua are both up 21% and 27% respectively from last year levels.  Rough rice sales have been the bright spot in trade as milled sales are 26% behind last year.  Total long-grain sales are 5% ahead of last year for the week ending July 22nd.

The next USDA supply/demand and Crop Production reports will be released on August 12th.  Also, FSA is expected to release its first report of the year on certified crop acres.  Following the early June flooding in south Arkansas, questions remain regarding failed acres on a number of crops, including rice.  Ideas that some rice acreage was lost may be part of the fuel behind the futures rally seen since July 12th.  Certainly the anticipation of sales to Iraq was key as well.

Shot in the Arm for the Industry: 120,000 Tons Sold to Iraq

Sarah Moran, USA Rice.  Sales of 80,000 tons of U.S. rice to Iraq have just been announced by ADM (subject to letter of credit approval), and an additional 40,000 tons was sold by Supreme Rice, also pending letter of credit approval.  They are the first sales to Iraq in two years, arriving at the Umm Qasr port in October and November.

Earlier this month, USA Rice signed a memorandum of understanding (MOU) with Iraq’s new purchasing entity, Al Awees, to provide certainty to a top U.S. rice export market.

“This MOU, which builds upon the initial MOU between the U.S. and Iraqi governments, calls for purchases of 200,000 tons of U.S. rice annually,” said Bobby Hanks, USA Rice Chair.  “It took a bit of time for us all to understand this new system in Iraq, but now we are well positioned to provide Iraq with high quality U.S. rice, which Iraqi citizens appreciate.”

Preceding this new MOU, seven Senators and twelve Congressmen wrote to the U.S Ambassador in Iraq, Matthew Tueller, requesting urgent attention to the recent changes in procurement and highlighting the importance of the Iraqi market to many of their constituents.  Ambassador Tueller swiftly conveyed these concerns directly with Iraq Prime Minister Kadhimi and Minister of Trade Al-Jabouri.

“We greatly appreciate Ambassador Tueller’s efforts and would also like to especially thank Senator John Boozman and Congressmen Rick Crawford, Bennie Thompson, and Clay Higgins for leading efforts to find a workable solution for U.S. rice farmers and the industry,” continued Hanks.  “I’d also like to thank my own representatives, including Senators Cassidy and Kennedy, for their efforts here in helping Louisiana farmers.”

Iraq has been a top market for U.S. rice for decades, providing up to 150,000 metric tons in recent years.  For the past two years, Iraq has not imported any U.S rice amid drastic revenue shortages, given that crude oil exports account for 90% of Iraq’s revenue and the low prices of oil in 2020.


Row Crops Radio Podcasts

Check out these podcast episodes by following the link or by listening to them on Arkansas Row Crops Radio wherever you listen to podcasts.

Rice & Advice, Ep. 05: Rice Fungicide Timing & Decision-Making (7/30/21)

Weeds AR Wild, Ep. 20:  Drift and New Weed Control Technologies Update (7/21/21) – discussion of Rogue herbicide at 13:00 mark


DD50 Rice Management Program is Live

The DD50 Rice Management Program is live and ready for fields to be enrolled for the 2021 season.  All log-in and producer information has been retained from the 2020 season, so if you used the program last year you can log in just as you did last year.  Log in and enroll fields here:


Use the Arkansas Rice Advisor Internet App!

The Arkansas Rice Advisor site functions like an app on your mobile device.  There you can readily access the DD50 program, rice seeding rate calculator, drill calibration, fertilizer and N rate calculators, publications, and more.


Additional Information

Arkansas Rice Updates are published periodically to provide timely information and recommendations for rice production in Arkansas.  If you would like to be added to this email list, please send your request to

This information will also be posted to the Arkansas Row Crops blog ( where additional information from Extension specialists can be found.

More information on rice production, including access to all publications and reports, can be found at


We sincerely appreciate the support for this publication provided by the rice farmers of Arkansas and administered by the Arkansas Rice Research and Promotion Board.

The authors greatly appreciate the feedback and contributions of all growers, county agents, consultants, and rice industry stakeholders.


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