Fungicide Questions in Wheat and Rye (06/02/22)
Winter Wheat and Spring Wheat
The decision to apply an early season fungicide to winter wheat is fast approaching. Although not as frequently observed, some of the earliest planted spring wheat in the state is at late-tillering stage and may receive a fungicide in the next 10 days. The cool wet weather in the state has provided favorable conditions for tan spot and Stagonospora leaf blotch and several infection periods have occurred in the past two weeks (as indicated by the NDSU Small Grain Disease Forecasting website). If you are considering a fungicide application, there is a great resource pertaining to fungicide selection found on the Crop Protection Network’s website:
Fungicide Efficacy for Control of Wheat Diseases
The publication is the result of a multi-state effort that presents efficacy of fungicides on wheat diseases in the US. Specifically, the publication provides the Fungicide Resistance Action Committee (FRAC) group(s), active ingredient(s), trade name, rate range, and level of efficacy for eight wheat diseases.
One of the most common questions pertaining to a fungicide at tillering pertains to yield response (or yield protection). First, remember the fungicide will only protect leaves made available at the time of application and will not provide season-long protection. Also, the observed yield response from an early-season fungicide application depends on several factors. These include the amount of disease resistance in the variety planted, environmental factors, and agronomic practices. Each year I update a data set that observes the yield trends from a fungicide application at tillering under diverse field environments. In table 1, I have summarized the data from 85 small plot trials and categorized them into four disease risk environments. Disease risk environments were determined using information pertaining to variety resistance, previous crop, tillage practices, dew periods, rainfall, and timing of disease onset. You will notice the yield response from an early-season fungicide (regardless of fungicide used) protects more yield under higher disease risks. For example, let’s assume we have a 55 bu/a wheat crop. In a very low disease environment, the yield response is less than 0.01 bu/A. However, in a moderate to high disease risk environment, the yield response would range from 2.3 to 2.5 bu/a.
Winter Rye
I have received reports of winter rye starting to head in the state and I have had a few conversations about protecting the rye crop from Fusarium head blight (FHB) and foliar diseases. Winter rye is susceptible to Fusarium head blight, but we have limited information pertaining to variety susceptibility in rye varieties commonly planted in North Dakota. Using scab risk model estimates intended for wheat, most of the state is in low to moderate risk for FHB. It is likely that risk will increase for some areas of the state in the coming week as a result of recent rain events. Fungicides can be effective for managing both leaf diseases and Fusarium head blight in rye. Field research conducted at the University of Kentucky on rye have found that single applications of Caramba or Miravis Ace made at early-anthesis or five days after early-anthesis provided significant suppression of both FHB and leaf diseases (data available at:
Rye Crop and Disease Management in Kentucky Report on 2018-2019[AT1]
Rye Crop and Disease Management in Kentucky 2019-2020
A final note about fungicides in rye. Remember that not all FHB fungicides labeled in wheat are labeled in rye and applicators need to follow directions on the label.
Extension Plant Pathology, Cereal Crops
