Small Grain Fungicides

Fungicides are available for both early season control of tan spot and for later season control of all three leaf spot diseases. NDSU research has shown modest (2- to 6-bushel) yield responses with application of reduced rates of fungicide to wheat for control of early season tan spot when: 1) wheat was planted into wheat residue, 2) a susceptible to moderately susceptible variety was grown and 3) when spring rains favored disease development. Early season application is not recommended as a standard practice in the absence of disease or favorable environment, and reduced-rate applications are not recommended in other crops.

Protectant fungicides, such as those containing mancozeb (Dithane products, Manzate 200, Manex II, Penncozeb products, Manzate 75, etc.), copper (Kocide, Champ) or combination products of mancozeb + copper (ManKocide) provide a layer of protection against infection if they are present prior to the spores landing on the leaf surface. They need to be in place before infection occurs. Protectant fungicides generally are effective only from seven to 10 days because they degrade with rain and sunlight. Two applications of protectants may be needed for longer season protection, and they generally need the addition of a spreader/sticker product.

Locally systemic fungicides, such as triazoles and strobilurins, have very good to excellent activity against the leaf spot diseases of wheat. Products with mixtures of these two classes of chemistry also are available. For some, half the full label rates have been used for early season tan spot control, generally applied at the four- to five-leaf stage, but this is a practice only recommended for tan spot of wheat under certain environmental conditions: i.e. wet weather, susceptible variety and some wheat residue present. Check fungicide and/or herbicide labels for allowed tank mixes for this early season use. Full label rates of fungicides generally are applied to protect the flag leaf from boot stage (Feekes 10) to flowering (Feekes 10.51). The flag leaf is an important source of nutrients transmitted to kernels for grain fill.

Also see North Dakota Field Crop Funigicide Guide for updated information on registered fungicides.