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Selecting a Fungicide for Early-Season Wheat Diseases (05/27/21)

The decision to tank mix a fungicide with an early season herbicide will be occurring soon. The diseases targeted by this fungicide application are fungal leaf spots, including tan spot (primarily), Stagonospora nodorum blotch and Septoria tritici blotch.

The decision to tank mix a fungicide with an early season herbicide will be occurring soon. The diseases targeted by this fungicide application are fungal leaf spots, including tan spot (primarily), Stagonospora nodorum blotch and Septoria tritici blotch. There are several very good to excellent fungicides that can be used to manage fungal leaf spots and efficacy information can be found in the NCERA-184 fungicide efficacy table. As a reminder, a fungicide will only protect leaves that are available at the time of application, and any “new” leaves will be left unprotected. If you are interested in the phytomobility of a fungicide (movement in plant tissues), please review the information in a recently published Crop Protection Network Web Book: Fungicide Use in Field Crops.

Wheat producers may also be asking the question if an early-season fungicide is necessary this year due to perceived low disease risk? Research data on early season fungicides in different disease risk environments suggest that the yield response observed in a low disease risk environment is 0.1%, and 3% for a moderate disease risk environment. For these studies, a low disease risk environment was defined as a susceptible wheat variety seeded after a cultivated broadleaf crop with infrequent periods of moisture/dew. A moderate disease risk was defined as seeding a susceptible wheat variety into cultivated wheat ground, with cool weather and sporadic moisture/dew events. Currently, I would consider most of the state in low to moderate fungal leaf spot risk, and yield expectations from an early season fungicide will be modest, especially if a moderately resistant variety (score of 2 to 4 in HRSW guide) was seeded. However, conditions can change quickly and the NDSU Small Grain Disease Forecasting Model can be used to help estimate fungal leaf spot risk.

 

Andrew Friskop

Extension Plant Pathology, Cereal Crops

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