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Response from an Early Season Fungicide in (05/07/20)

A common practice that will occur in the coming weeks is tank mixing a fungicide with the first herbicide pass in wheat (Figure 1).

A common practice that will occur in the coming weeks is tank mixing a fungicide with the first herbicide pass in wheat (Figure 1). The application of a fungicide at this wheat growth stage is primarily targeting early-season residue borne diseases such as tan spot. However, one common question that arises during this time of year is what to expect (yield) from this fungicide? I have provided a few data sets that highlight the yield response of an early-fungicide in wheat.

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2015 Fungicide by Variety Trial

The yield response of a fungicide can vary depending on disease risk and variety used. A good example of this was a fungicide by variety trial conducted in 2015 at Carrington (Blaine Schatz) and Fargo. Five HRSW varieties were used to compare the impact of a fungicide application at tillering (Table 1). The Carrington location had a much higher disease risk as it was seeded onto minimally tilled wheat ground, whereas the Fargo location was seeded into cultivated soybean ground. Although this is only one year of data from two locations, these data sets demonstrate that a greater yield response occurs when there is a higher level of disease risk.

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Larger Data Set

A total of 59 replicated fungicide trials that included a tillering fungicide application were conducted in Fargo from 2008-2015. Disease levels varied in the trials and were categorized into three disease risks (low, moderate and high) based on environmental conditions and production practices. Based on this data set (when compared to a non-treated control), the mean positive yield response for an early-season fungicide was 0.1% for low disease risk, 3% for moderate disease risk, and 4% for high disease risk. Another way to interpret this data is if a 65 bu/A wheat crop is expected, the potential yield response from a fungicide at tillering in moderate to high disease risk environment is approximately 2-3 bushels. This data set also supports that a greater yield response from a fungicide will occur in higher disease risk environments.

What to Use?

There are several fungicides labeled that are effective on fungal leaf spot diseases of wheat. For more information, please consult the 2020 North Dakota Field Crop Plant Disease Management Guide or use the NCERA-184 fungicide efficacy table. As a reminder, fungicides are best used in a preventative manner and will only protect available leaf tissue at time of application. Also, it is important to remember how a fungicide moves in leaf tissue. Most systemic fungicides are locally systemic (moves short distance from droplet), translaminar (moves from top side of leaf to the underside), or moves upward with xylem to a leaf tip. As the wheat crop progresses, new unprotected leaves will emerge, so scouting is one of our best tools to stay on top of disease progression.

Andrew Friskop

Extension Plant Pathology, Cereal Crops

This site is supported in part by the Crop Protection and Pest Management Program [grant no. 2017-70006-27144/accession 1013592] from the USDA National Institute of Food and Agriculture. Any opinions, findings, conclusions, or recommendations expressed are those of the website author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.

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