Today's Date: 2020-07-06

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Tan Spot 

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Plant Pathologist Commentary: Small Grains Disease Update 06/29/2020

In my travels last week across southern Minnesota, I found little to no disease in the spring wheat trials or fields that I walked. I found net blotch in one of the barley varieties (Pinnacle) that is very susceptible to this foliar pathogen and here and there was some tan spot in some of the winter wheat varieties. The most common and widespread, however, was BYDV. In production fields, these virus infections were the typical small circular patches or individual plants that showed the typical bright yellow flag leaves. In individual plots, these were often individual plants along edges of the plot. I found no leaf or stripe rust and it was a bit too early to see whether there were any of scab infections.

The risk of FHB increased in especially north of US Hwy 2 and across much of southern Minnesota (south of US Hwy 12), while conditions for tan spot remained high across much of the state. The notable exceptions for increased risk for FHB infections, or the foliar diseases, were the southern Red River Valley and west-central Minnesota. The very dry conditions I encountered in my trials near Benson explain why. There simply wasn't and still isn't enough moisture in the whole system to have leaf wetness periods long enough for any of the diseases to create initial infections.

The predicted heat for the coming week combined with the forecast of scattered thunderstorms will likely mean that the risk for FHB will remain high for varieties that are rated very susceptible or susceptible to the disease in those areas that already have adequate soil moisture. The risk for FHB infections will likely be moderate for varieties that are rated moderately resistant or better. If your barley or hard red spring wheat crop reaches anthesis (Feekes 10.51) this coming week, you will need to make a decision whether you choose tebuconazole or one Prosaro/Caramba/Miravis Ace. The later three fungicides each improve suppression of FHB by about 15% to 20% over tebuconazole. All products will provide very good to excellent control of any of the foliar diseases.

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.