Today's Date: 2019-06-18

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Tan Spot 

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Plant Pathologist Commentary: Small Grains Disease Update 06/14/2019

Scouts continue to find tan spot in both winter wheat and spring wheat in their second week of scouting. There were no reports for Septoria spp. or leaf rust. The reported incidence and severity of tan spot increased a bit from the previous week. The risk assessment models mirror their findings as conditions for septoria and leaf rust were not as favorable as they have been for tan spot.

As temperatures and relative humidities are forecasted to increase in immediate weather forecast so are the risk for all three leaf disease complexes are also trending higher.

If you have not completed weed control in spring wheat yet, consider tank-mixing half a labeled rate of a registered fungicide with your weed control program to control early season tan spot in spring wheat when tan spot can found in your fields. Winter wheat is flowering or Feekes 10.51 in the southern half of Minnesota. To date, the risk model for FHB continues to be trending low, largely because of the cooler temperatures rather than the absence of precipitation. The immediate forecast continues to indicate a low risk of FHB.

However, the application of a fungicide at Feekes 10.51 to suppress FHB is the final opportunity to controls leaf diseases like tan spot, Septoria spp., and leaf rust. Previous research has shown that control of the leaf diseases usually pays in the case of winter wheat. Therefore, I suggest you scout your winter wheat now and consider a fungicide application if any leaf diseases can be found in the lower canopy.

Important Note Important Note: Please review Terms of Use before utilizing this site. The leaf disease models available on this website are courtesy of NDSU. Infection happens when an infectious pathogen contacts a susceptible plant in a suitable environment. To find out if the previous day contained an infection period, the models use hourly high-resolution weather data provided by Iteris, Inc. The leaf disease forecaster is intended to be used in steps, which are described here, that work together to maximize your potential economic return by protecting the health of the top two leaves. It is important to note that in order for the forecasting model to work as intended, the disease-causing agent must be present, which requires field scouting as described here.