Arkansas Rice: Scattered, Smothered, and Covered

Photo: University of Arkansas

Scattered rains occurred across the northeast portion of the state this week.  Once again, a welcome sight for the region with some receiving several inches of rainfall.  The central and southern areas have been less fortunate, with continued extreme dry conditions.  Water management continues to be a struggle for many in that part of the state as we approach heading on more and more acres.

While temperatures and humidity are on the miserable side for people at the moment, the rice is loving the weather.  The first fields in the state have begun to head over the past week or so.  The extended temperature outlook remains moderate (for July) which would be very welcome to keep crop quality high.

However, the end of July into early August is traditionally our hottest period of the year, and much remains to be seen about what conditions will be then.

As usual at this point in the season, the oddball field occurrences start to happen.  Questions about possibly fertility issues / deficiencies remain common.  You always hear us say early in the season “don’t guess, soil test” but this time of year it’s more “don’t guess, tissue test.”

In cases of pronounced deficiencies, we can often point you in the right direction with a quick field visit or even sometimes from a few pictures.  But some of the oddities occurring right now are not extremely pronounced and it hasn’t been uncommon for tissue testing to point us in the right direction that maybe we weren’t originally leaning.

Contact us or your county agent for help if you have fields that look questionable, don’t be too quick to pull the trigger on an application that may be an unnecessary expense.

Rice 50% Heading

Click Image to Enlarge

NOAA 7 day precipitation forecast

Fig. 1.  NOAA 7-day Precipitation Forecast. Click Image to Enlarge

Managing Kernel and False Smut in Rice

In flooded or furrow irrigated rice, most cultivars including the hybrid are susceptible or moderately susceptible to kernel or false smut or both.  Generally, under favorable weather conditions, kernel and false smut are severe in late-planted susceptible rice grown in a field with a history and/or having dense canopy and applied with excessive nitrogen fertilizers.

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Appropriate cultural practices are highly recommended to reduce the severity levels of both diseases.  Scouting for kernel or false smut is not helpful to plan for fungicide application.  Once the diseases appear, it is already too late for fungicide application.

The recommended fungicides are protective and need to be applied between early-boot to mid-boot (Figure 2).  Mid-boot is the optimum timing.  The benefit from fungicide use continues to decrease if applied after mid-boot, and applying at boot split (Figure 3) is too late.

Triazole fungicides containing Propiconazole (Tilt equivalents) or Difenoconazole are the commercially available fungicides to suppress these diseases.  When the fungicides are applied at the correct timing and rate using an adequate water volume, 90% to 95% suppression can be attained in Kernel smut.

While the false smut fungus is less sensitive to the chemistries, research has shown 50% to 70% suppression using triazole fungicides.  A minimum of 6 fl oz per acre rate of tilt or tilt equivalent is recommended.  To suppress kernel and false smut, triazole fungicides such as Tilt, Bumper or Propimax can be used.  If pre-mixes are desired Quilt, Quilt Xcel or Amistar Top can be used.

When Stratego or Flint Extra is desired, adjust the tilt equivalent to at least 6 fl oz per acre rate.  Check out the blog on rice fungicides and mix rates.  Read fungicide labels carefully before mixing or application.  Labels are the rule.

Sometimes the recommended fungicide timing for smut suppression may align with the sheath blight at the threshold level.  In such situations, combination fungicides may be used to address the three diseases together and save additional application costs.  For adequate canopy coverage, a minimum of 5 or up to 10 gallons of water per acre is encouraged.

Early to mid-boot is the optimum timing for kernel and false smut fungicide application

Fig.2. Early to mid-boot is the optimum timing for kernel and false smut fungicide application.

Applying protective fungicides after mid-boot to suppress kernel or false smut is too late

Fig. 3. Applying protective fungicides after mid-boot to suppress kernel or false smut is too late.




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