Arkansas Rice: Crop Progressing Quickly, Leaf Blast Widespread

    Photo: University of Arkansas

    Industry News

    While the news is spreading far and wide, it’s still worth mentioning the signed phytosanitary agreement between the U.S. and China.  This is the first step in opening up a new market for U.S. rice.  While it will still be some time before the full effect of this event is realized and U.S. rice actually reaches China, it is a major step for the U.S. rice industry.

    Crop Progress

    “Warp speed, Mr. Sulu!”  The rice crop is moving at a rapid pace with the hot, sunny days of late.  This is a big positive to maximizing grain fill as we enter heading.  What it can’t do is reverse the likely reduced number of kernels formed back during the overcast month of June.  However, if we can fill all the kernels we did make we might not feel the burn too bad.

    The upcoming forecast is one that should give us mixed emotions.  It seems the heat will break some over the next 14 days, particularly the nighttime temperatures.  However, there is rain the forecast to go along with it, and that’s bad timing for potential issues with blast, sheath blight, and bacterial panicle blight.

    Be diligent in scouting for diseases and carefully read the disease update below.

    Fig. 1. Mornings are hot with heavy dew.

    Fig. 2. Current 14-day forecast. Click Image to Enlarge

    Arkansas Rice College is August 3rd

    The 2017 Rice College will be held at the Rice Research & Extension Center at Stuttgart, AR on Thursday, Aug. 3.  For more information and to register go here:  2017 Rice College Information & Registration.

    Deadline for registration is July 26.  Cost is $75.  No on-site registration will be allowed the day of the event.

    Rice Disease Update

    To date, we have received reports of leaf blast in 12 Arkansas counties including Woodruff, Monroe, Perry, Pulaski, Lawrence, Clark, St. Francis, Randolph, Jackson, Desha, Clay, and Greene.  Cultivars reported include Jupiter, LaKast, Diamond, Francis, Titan, Diamond, Rex, Roy J, and CL151.

    Although the high temperatures appeared to slow down leaf blast, the morning fog and dew are still of concern.  All these varieties have been known as susceptible to leaf blast.  However, there has not been a report of leaf blast blowing up up to leaf burndown so far.

    If leaf blast is detected early in the season on a susceptible variety neck blast is often predicted and at least a one-time protective fungicide is justified. However, the absence of or inability to detect leaf blast on a susceptible variety in a field with a history of blast does not guarantee that neck and/or panicle blast won’t show up later in the season.

    Blast pathogen spores can be carried by wind and unexpected infection can happen under favorable weather conditions and inadequate water and fertility management.

    Continue scouting for leaf blast.  Leaf blast is often managed by increasing flood depth.  However, if a fungicide application is needed, it can possibly be aligned with the need for smut management.  However, protective fungicides for neck blast should generally need to be managed separately from smuts.

    The optimum 1st application timing for managing neck blast is late boot to 10% heading. The percent heading refers to how far the heads have moved out of the boot NOT percentage of plants headed across the field. In fields where smut concerns are minimal and the blast treatment is made at late boot, some smut suppression can be achieved but efficacy may be greatly reduced compared to earlier application timings.

    Fungicide applications to control neck blast are generally too late for best smut suppression.

    The 2nd application for neck blast protection is at 50-70% head out.  Note that the 1st application is to protect the necks of primary tillers and the 2nd application which usually follows 5-7 days later is to protect the secondary tillers.

    It is your judgement call to do one or two applications for neck blast protection.  However, it is not recommended to make blanket application of fungicides on every variety, every location, and every year – make application decisions on a case-by-case, field-by-field basis.

    Remember also late-planted susceptible rice is more prone to blast than early planted rice.  Often there is higher probability for the early-planted susceptible rice to escape or to have less blast than the late-planted rice.

    Fig. 3. Sheath blight and blast together. Click Image to Enlarge

    Sheath Blight

    So far, sheath blight has been moving very slow and several early planted rice fields appear to have escaped the disease.  However, with this heat a single shower may change the picture.  Therefore, keep scouting for sheath blight as well.

    Fungicide applications for sheath blight are recommended at a threshold of 35% or more positive stops in susceptible cultivars and 50% or more positive stops in moderately susceptible cultivars.  You would also consider fungicide applications at early heading if the upper tow or three leaves are threatened, but you must adhere to the 28-day pre-harvest interval.

    Bacterial Panicle Blight

    So far, no one talks about it and there have been no reports in already headed rice.  From our observations and studies, this disease is aggravated by rain showers, particularly windy rain on top of high day and night temperatures.  To date, we have no chemical options for bacterial panicle blight to be used in the USA.  Planting clean seeds, early planting, adequate seeding rates and levels of nitrogen and potassium fertilizers are known recommendations so far.

    Kernel Smut and False Smut

    It is early and hot to see false smut in headed rice.  The false smut fungus is relatively less sensitive to propiconazole fungicides and is more severe in late planted rice.  Kernel smut likes hot weather if associated with rain and is more senstive to fungicides.

    Fig. 4. Rice stink bugs are still out there.

    Based on the susceptibility of your cultivar, field history, your management related to water and fertilizations, if you decide to apply protective fungicides for blast, kernel smut, and false smut, then do it right!  Right means application of the correct fungicide at the correct timing, correct rate, and correct volume of water for adequate coverage.

    Management Key:

    Rice stink bug (RSB) thresholds are:

    • 5 RSB per 10 sweeps the 1st 2 weeks after 50% heading.
    • 10 RSB per 10 sweeps the 2nd 2 weeks after 50% heading.

    Enroll Fields in the DD50 Program to Help Time Management Decisions

    The DD50 program can be found here.  Please let us know if you have any questions or encounter any problems.

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