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Fungicide Selection for Early-Season Wheat Diseases (05/24/18)

Winter wheat is starting to tiller and spring wheat is emerging or in the early leaf stages. With the first herbicide pass approaching, growers will often consider tank-mixing a fungicide for early-season disease control.

Fungicide Selection for Early-Season Wheat Diseases

Winter wheat is starting to tiller and spring wheat is emerging or in the early leaf stages. With the first herbicide pass approaching, growers will often consider tank-mixing a fungicide for early-season disease control. This will often prompt questions on fungicide selection, especially with the number of fungicide products that are available. With that in mind, here are a few things to consider when choosing a fungicide.

Diseases Being Targeted

The early-season fungicide primarily targets residue borne diseases (Figure 1) such as tan spot (most common in North Dakota), Septoria blotch and Stagonospora blotch. Therefore, make sure to choose a fungicide with an active ingredient that can suppress these diseases. There are several fungicides that have very good to excellent activity and each year wheat pathologists in the United States (NCERA-184 – North Central Regional Committee on Management of Small Grain Diseases) create a table with fungicide efficacy information.

Disease Risk and Fungicide Movement

Greater disease risk is associated with no-till fields that have a short rotation away from wheat. The fungal leaf spot pathogens can survival several years on wheat stubble (at least two years) that is left undisturbed on the soil surface. Methods to destroy wheat residue can significantly reduce pathogen viability. Also, it is important to remember that most fungicides used in wheat are locally systemic or translaminar (move from topside to underside of leaf). In other words, a fungicide will not protect leaves that have emerged after an application has been made, and fields need to be scouted to assess disease risk throughout the growing season.

Fungicide Stewardship

We do not have fungicide resistance issues for wheat pathogens in ND, but it is always important to rotate fungicide mode of action (MOA) to delay or avoid issues in the future. The most popular groups of fungicides in wheat are triazoles/DMI (FRAC 3), carboximides/SDHI (FRAC 7) and strobilurins/QoI (FRAC 11). Given the limited number of fungicide groups, it is important to reduce the reliance on a single MOA. For example, if a triazole is used early in the season, the same fungicide group will be used again if a Fusarium head blight (scab) application is warranted at early-flowering.

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Andrew Friskop

Extension Plant Pathology, Cereal Crops

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