As wheat starts to green-up across the state, questions are coming in about the benefit of early fungicide applications.
Research at K-State and in other regions continues to demonstrate that it is often possible to achieve high levels of foliar disease control with a single fungicide applied between flag leaf emergence and heading growth stages. The yield response to this later fungicide application is influenced by the level of disease risk (amount of disease and predicted weather conditions), variety resistance to the most threatening fungal diseases, yield potential of the crop, foliar fungicide efficacy, and other factors.
Fungicides can also be applied as an early application made between “spring green-up” and jointing. This application may provide some yield benefit in some fields and years. It’s important to note that an application during these early stages of crop development is not a substitute for a flag leaf application, as any leaf that emerged after the application will not be protected. Early fungicide applications may result in small yield advantages due to a reduction in early disease establishment in the lower canopy. This may be particularly true for “leaf spot diseases” such as tan spot or Septoria leaf blotch that survive in wheat residue and can establish early in the year. Yield benefits are most likely in wheat fields planted back into wheat stubble and when weather conditions are wet enough to favor fungal disease development.
If deciding to make an early application, it is important to factor that into the full season fungicide program. Many active ingredients have use restrictions, where a limited amount of an active ingredient can be applied during a single season. It is important to make sure the early fungicide does not limit options for fungicide applications at flag leaf (which have the potential for higher yield protection in conducive disease years).
Advantages and limitations of split applications
These are some advantages to making an early application:
The limitations of early-season fungicide application include:
Product rates and restrictions
Producers considering the use of split applications must pay close attention to label restrictions. Every active ingredient in a fungicide has a maximum total amount that can be applied during the season.
For example, if an early application of a generic form of tebuconazole is applied at 4 oz/acre, a subsequent application of any fungicide containing tebuconazole alone or in combination with other ingredients (e.g. premix) around heading could put you over the limit for the crop season. Thus, be sure to read the label to determine the maximum amount of a chemical that can be applied in a single season and the exact amount of a chemical(s) that is in a fungicide.
For information on the efficacy of different foliar fungicide products, refer to K-State Research and Extension publication: Foliar Fungicide Efficacy Ratings for Wheat Disease Management 2023, EP130.
The main conclusions we can draw from recent studies in Kansas and Oklahoma are:
KSRE publication Foliar Fungicide Efficacy Ratings for Wheat Disease Management 2023.
For information on assessing the need for wheat foliar fungicide, refer to KSRE publication Evaluating the Need for Wheat Foliar Fungicides, MF3057.
Another publication providing good information, from which a few excerpts were used in this article, is Oklahoma State University’s Split Versus Single Applications of Fungicides to Control Foliar Wheat Diseases, PSS-2138.
Kelsey Andersen Onofre, Extension Plant Pathologist Romulo Lollato, Wheat and Forages Specialist
Erick DeWolf, Plant Pathologist
Romulo Lollato, Wheat and Forages Specialist