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Issue No. 11, Article 5/June 4, 2004

Update on Fusarium Head Blight (Scab) and Other Diseases of Wheat in Illinois

Diseases continue to appear in Illinois wheat fields. Leaf and stripe rusts have been reported at minor levels, Stagonospora and Septoria leaf spots are occurring, and the yellow-red leaf discoloration and stunting caused by barley yellow dwarf have developed. It's too late to manage these diseases this year, but keeping notes on which problems occurred may help with management and variety selection in the future. Fusarium head blight, also called scab, is perhaps the biggest problem in many wheat fields at this time.

Fusarium head blight (FHB) has developed in many areas of Illinois, and now is the time to scout most fields to determine the incidence of this disease. The symptom that is most easily seen is premature bleaching of several or all spikelets on a head of wheat. By general reports, FHB is more common in the northern half of Illinois than the southern half this year. In 2003, the opposite was true. In southern Illinois this year, results from an informal survey indicate that FHB incidence in most fields ranged from 2% to 8%, whereas in 2003 it was closer to 20% to 30% in the same areas. In naturally infested FHB research plots grown in corn residue near Urbana this season, preliminary results indicate scab incidence is more than 25% in many plots. FHB levels near 20% have also been reported near Bloomington.

Fusarium head blight (scab) of wheat near Urbana in 2004.

Because FHB development is very strongly favored by wet weather conditions when the wheat is flowering, the differing amounts of FHB in different locations and different years are most readily explained by weather conditions. For additional information on FHB symptoms and weather conditions that favor this disease, please refer to articles in issue no. 5 (April 23, 2004) of the Bulletin.

Information was presented in those articles regarding a temporary emergency Section 18 label for the fungicide Folicur for FHB control and a new prediction system for FHB on wheat. The label for Folicur has expired for 2004, and we look forward to getting information from Illinois to determine how much was used and how well it worked for reducing FHB and the mycotoxin deoxnavalinol (also called DON or vomitoxin) in grain. The FHB prediction model can still be useful his year. You can see how well the weather-based model worked this year for predicting FHB in any area of the state. Go to the prediction system (http://www.wheatscab.psu.edu/), choose a location, and choose the dates when wheat was flowering. The system will then give a risk level for FHB development at that location and help us understand how well the model worked for Illinois conditions.

In addition to reducing grain value due to DON contamination, severe FHB can prevent or reduce seed filling and cause yield losses. In some cases, DON levels may be reduced by harvesting dry grain as soon as it is mature and keeping it dry, and by adjusting the combine to remove the lightweight kernels infected with FHB in addition to the chaff.--Dean Malvick

Dean Malvick

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