Louisiana Rice: Changes in Available Fungicides

    Rice sheath blight. Photo: University of Arkansas

    Fungicides are important tools in rice disease management. All too often sheath blight, blast, grain smuts or Cercospora require a fungicide application to reduce damage below economic levels. Fungicides are specific to what diseases they control, along with the growth stage they are applied at to be effective.

    Therefore, knowing what diseases are present in your field, selection of the most active fungicides against those diseases, and applying them at the correct growth stage are critical for effective disease control. Several changes in fungicide availability will impact which fungicides and how you use them in 2021.

    Stratego, which is a combination of Trifloxystrobin and propiconazole, will not be marketed by Bayer this year due to label changes that prevent it from being applied at heading, which is the most important timing for blast. They will be marketing Trifloxystrobin, as Flint, which will be applied at 3.6 to 4.7 oz/A and can be applied from boot to heading.

    To obtain the same spectrum of disease control activity as Stratego, farmers will have to add 6 to 10 oz/A of propiconazole with Flint as a tank mix. If your target is blast, kernel, or false smut, the propiconazole must be applied separately at booting, and the Flint at heading.

    Another rice fungicide, which I have not discussed much but was marketed last year, is Artisan, which is a premix of flutolanil and propiconazole. Flutolanil is the active ingredient in Elegia which has good activity against both the wild-type and strobilurin-resistant sheath blight fungus strains.

    Elegia is used at 32 oz/A where the labeled rate of Artisan is 40 oz/A. The propiconazole in Artisan increases activity against Cercospora and the grain smuts. You can add propiconazole to Elegia and have a very similar activity.

    Remember that the maximum amount of propiconazole at one application is 10 oz/A with a maximum of 12 oz/A per year. You can use two 6-ounce applications which is slightly more effective against sheath blight than a single 10-ounce application.

    Be careful how much propiconazole you add to the tank, especially with fungicides that already have propiconazole in them, so you do not exceed the maximum amount.

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