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Early Season Tan Spot (and Risk of Crop Injury When Tank Mixing Fungicides and Herbicides)

Scouts identified tan spot in many spring wheat fields across Minnesota last week. The incidence and severity was generally low. Weekly summaries of this statewide scouting activity that is funded by the Minnesota Wheat Research & promotion Council are forthcoming.

If you are considering controlling early season tan spot, please follow this link to an article that was published in Minnesota Crop News last spring. It describes how and when control of early season tan spot is warranted and lists fungicide choices and rates.

If you are considering tank mixing a fungicide with your herbicide program be aware that tank mixing can increase the risk of crop injury with certain combinations of herbicides and fungicides. Research between 2004 and 2006 at the University of Minnesota, showed that combinations of the broadleaf herbicide bromoxynil with several grass herbicides and fungicides can increase the risk of crop injury, especially with cooler weather. The injury is caused by bromoxynil and is temporary with no effect on grain yield. There is, however, a small risk of reduced control of wild oats as the injury that is visible on wheat can also be found on the wild oats. It was postulated that the bromoxynil injury reduced uptake and/or translocation of the grass herbicide, ultimately resulting in a couple percent reduction in control.

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