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05
Jul
2016
Timing for application of protective fungicides to suppress rice kernel and false smut
Author: Yeshi Wamishe, Extension Rice Plant Pathologist

By Yeshi Wamishe, Extension Rice Pathologist

Rice fields having history of kernel and/or false smut applied with excessive nitrogen are prone to smuts in susceptible rice. Unfortunately under favorable conditions, most rice cultivars are susceptible including hybrid rice. False smut often is more severe in late planted rice since it is favored more by lower temperatures than needed for kernel smut.

If preventative fungicide application against false and or kernel smut is warranted, triazole fungicides containing propiconazole (tilt equivalents) are still the existing options. Kernel smut is more sensitive to the fungicides with up to 90% to 95% suppression provided the rate, timing and coverage are done right. Well managed fields benefit the most from fungicide application. False smut can be suppressed up to 50% to 70% when application package is done correctly.

Fungicide Rate: In the past few years the tilt equivalent rate has been raised from 4fl oz to a minimum of 6 fl oz per acre.

Fungicide Timing: The correct recommended timing to apply protective fungicides against false and kernel smut is from early boot to mid boot developmental stage of the main tillers (Figure 1).  Fungicide applied after late boot are categorized as late. Fungicides applied at boot split are too late. (Figure 2). Fungicides applied after the heads are out are money wasted.  Fungicides applied earlier than boot stage are too early for the fungicides to stay effective until heading.

Figure 1. Early (left) to mid-boot (right) is the recommended timing for kernel and false smut fungicide application

Figure 1. Early (left) to mid-boot (right) is the recommended timing for kernel and false smut fungicide application

Coverage: For adequate coverage a minimum of 10 gallons of water per acre is encouraged to mix the fungicides.

Figure 2. Protective fungicide application to suppress kernel and/or false smut after late boot is not beneficial. It is already too late. Pictures show boot split (left ) and heading (right).

Figure 2. Protective fungicide application to suppress kernel and/or false smut after late boot is not beneficial. It is already too late. Pictures show boot split (left ) and heading (right).

 

Table 1. Strobilurin and triazole contents of commonly used fungicides for kernel and false smut suppression

Table 1. Strobilurin and triazole contents of commonly used fungicides for kernel and false smut suppression


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