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ISSUE 6  June 7, 2001



Tan spot is very common in wheat fields planted into wheat stubble. The fungal leaf spots have a dark brown center and a yellow to purplish halo around the center. In fields of wheat on wheat, the incidence of infection is from 80-100%, while in wheat fields planted into other crop ground the incidence is from 8-15%. Presence of tan spot is not surprising, considering recent weather in much of the state. The NDSU Small Grain Disease Forecasting model indicates that at Fargo, nine of the past 12 days have been favorable for tan spot infection.

For those fields in wheat stubble with abundant tan spot, an early season fungicide application of 1 lb mancozeb, 2 fl oz of Tilt, or 5 fl oz of Stratego may be warranted.

Bacterial blight on wheat was noted by Jan Knodel and Kent McKay at the North Central Research Extension Center in Minot, and by Extension Agent John Swenson in Griggs Co. High winds with accompanying rain showers allowed moving soil particles to cause wounds that allowed bacterial entry. The symptoms were some water soaking on the leaves and leaf tips, followed by some browning of the tissue. Bacterial blight should not affect the crop severely and should dry up when we get some sunny weather.

Some seed rot due to Penicillium and some common root rot have been observed in a few wheat fields where seed sat for a long time in dry soil (Penicillium rot) or where seedlings sat in wet soil for a long time (common root rot).



After a brief warm, dry spell in Kansas in mid-May, the weather there once again turned cool and wet which favored further development of stripe rust on some winter wheat cultivars in that state. Heavy infections of this rust developed in southern Kansas as of the end of May, and these infections may provide inoculum for infection in spring wheat states. We saw trace amounts of this rust last year, and if we would stay cool and wet here, we could see some stripe rust infections again. We will be monitoring for its presence in our survey efforts. Stripe rust spread and development is halted by warm, dry conditions.



The Small Grain Disease Forecasting web page and toll free telephone number are up and running for the season. Dr. Len Francl, NDSU Dept. of Plant Pathology, has put a slightly new look to the home page, and is providing leaf disease and scab information from 32 locations. Many locations show that conditions have been favorable for tan spot infection in the past 12 days. The web address is:


The toll free number is: 1-888-248-7357 or in Fargo area: 231-6601.



The Potato Disease Hot Line is up and running now, as of June 1. The Hot Line will provide updates every Monday, Wednesday, and Friday through the first week of September. The Potato Disease Hotline (Bravo/Quadris Blightline) is sponsored by Syngenta Crop Protection, and is provided through Drs. Neil Gudmestad and Gary Secor of the NDSU Plant Pathology Dept. The hotline provides information on severity values for potato late blight: The toll free number to call is: 1-888-482-7286

As of June 6, no late blight severity values had accumulated for any of the 14 non-irrigated production areas. Of eight irrigated sites, several sites had accumulated some low severity values.

The same information is available at the Plant Pathology Dept.ís potato disease web site:


The above web site also provides additional information on other diseases and potential insect problems during the growing season.

Marcia McMullen
Extension Plant Pathologist


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