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    Arkansas Rice: High Yield Disease, A Concern That’s Not an Issue; Leaf Blast Sneaking In

    High Yield Disease of Rice

    As most rice is now into reproductive growth, all random things are showing up.  Sulfur and potassium deficiencies have begun to appear, along with some hydrogen sulfide toxicity.  Delayed phytotoxicity is still an issue on some recently flooded fields as well.

    Aside from these, I’d like to point out one repeated concern this week that isn’t necessarily an issue.  Fig. 1 shows what has been termed “high yield disease” in the past.  Most often this occurs on the second leaf down from the top when rice is in reproductive growth and plants are growing rapidly.  These leaf tips may have a nutrient imbalance as the plant draws mobile nutrients from the leaves.

    Anytime you see anything like this, it is still wise to examine the whole plant, including roots, to be sure nothing else is going on.  If this is on all leaves or more excessive, it could be an indication of an underlying issue.  Reports so far have only been of the high yield disease type.

    High yield disease of rice

    Fig. 1.  “High yield disease” in rice.

    Rice Leaf Blast Sneaking In

    No doubt, it’s time to scout for leaf blast in Arkansas commercial rice fields with a history planted with susceptible (S) or moderately (MS) varieties.  Historically leaf blast starts mostly between the 2nd and 3rd week of June.  In 2022, the 1st report came in on June 27 from Arkansas County on Titan.  It appears dew period is long enough to initiate spore germination.  However, the heat appears a little high.  But we know the blast fungus is versatile and easy to adapt.

    Rice News on AgFax


    With rain in a forecast and overcast in blues, conditions may get favorable for rice blast progress.  Moisture fuels the disease.  The message is to keep on scouting.  As seen in Table 1, most of our conventional rice varieties grown in Arkansas are either susceptible (S) or moderately susceptible (MS).

    Where to Scout:

    At tree lines, dry field edges, levees, and spots in the field with greener canopy due to excessive nitrogen fertilization.

    Early Symptoms:

    Early symptoms may be confusing.  They may look greyish-black spots.  You may find the typical symptoms of blast if you open the canopy to lower leaves.  Please go to last week’s blog article here to learn more about leaf blast.

    Later Symptoms:

    Leaf lesions are spindle-shaped and elongated with brown borders and grayish centers.

    Advantages of Scouting for Leaf Blast:

    To help in fungicide application decision in protecting the crop from neck and panicle blast.

    To reduce spore production and lessen disease severity later in the season.

    Leaf Blast Management:  For leaf stages of the disease, maintain proper flood level.  Infection levels tend to be less severe where flood water is maintained at adequate but not excessive depths.  Avoid excessive rates of nitrogen (Nitrogen amounts vary with cropping history, soil type, varieties, etc.).

    Note:  The table below is comprehensive and includes frequently seen diseases in Arkansas commercial rice fields to serve you in your management options including fungicide application decisions.

    Table 1.  Rice Variety Reactions to Diseases and Lodging.

    Cultivar

    Blast

    Sheath Blight

    Straight

    head

    Bacterial Panicle Blight

    Narrow Brown Leaf Spot

    Kernel Smut

    False Smut

    Lodging

    Black Sheath Rot

    Sheath Spot

    ARoma 17 MS MS S MS S S MR S
    CL151 VS S VS VS S S S S S MS
    CLL15 MS S MS S S S S MR MS
    CLL16 MS S S MR MS MS
    CLL17 MS S S
    CLM04 S MS MS S MS S S
    DG263L MS S S S MS
    Diamond S S MS MS MS S VS MS S S
    Jewel MS MS S MR MS MS MS
    Jupiter S S MS MR S MS MS S MR
    LaKast S MS MS MS MS S S MS MS S
    Lynx MS S MS S MR MS S
    ProGold1 MS S MS S MS S MS
    ProGold2 MS MS MS S MS MS MS
    PVL02 S S S S S VS
    PVL03 S S S MS MS MR
    RT 7301 MR MS R MR MS MS MS
    RT 7321 FP R MS MR MS S MS MS
    RT 7401 MR MS MS MS MS
    RT 7501 MR S MS MS S S MS
    RT 7521 FP R S R MS MS VS S VS
    RT XP753 R MS MS MR MR MS S MR S
    RTv7231 MA S VS
    Titan MS S MS MS MS MS MS MS



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