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Dean Malvick
Dean Malvick
Assistant Professor of Plant Pathology
Department of Crop Sciences
(217) 265-5166; dmalvick@illinois.edu
Fred Kolb
Fred Kolb
Professor of Plant Breeding
Department of Crop Sciences
(217) 333-9485; f-kolb@illinois.edu

Is Wheat Scab an Emerging Threat or Recurring Villain?

This presentation will be directed at understanding wheat head scab and foliar crop diseases in relation to crop rotation, modeling, and management. Interactions between previous corn crops and wheat scab and the importance of weather on disease development will also be discussed. Scab was a significant problem in the northern half of Illinois in 2004, and in 2003 this disease was a major problem in southern Illinois. New developments are underway to improve management of scab, and some of these developments may also pave the way to improved management of some foliar diseases of corn and soybean.

Topics to be discussed:
· Residue-borne diseases and interactions between crops and diseases.
· Factors that control scab development
· Management tactics for scab
· Predictive models for scab and other diseases
· Fungicides and resistant wheat varieties – results from 2004

Head scab, or Fusarium head blight, of wheat is caused by the fungal pathogen Fusarium graminearum. This disease can reduce yields, market grade, and quality through production of the mycotoxin deoxynivalenol (also called DON or vomitoxin) in the grain. A form of the same pathogen causes Gibberella stalk and ear rot of corn. This fungus overwinters on wheat, corn, and grass residues, and scab is favored by large amounts of these plant residues on the soil surface. Spores produced on residue are spread by wind and rain to wheat heads where infection occurs only at flowering during wet and warm weather.

The symptom of scab that is easiest to recognize is premature bleaching of several or all spikelets on a head of wheat. The fungus can produce high levels of DON in heads that do not appear to be heavily infected.

To minimize damage from head scab producers should choose cultivars with resistance to the disease and avoid planting wheat following corn. In addition, the foliar fungicide Folicur 3.6F® (tebuconazole), from Bayer Crop Science was available in 2004 for scab management of wheat in Illinois. Watch for news about a new label for its use in 2005. Results from numerous trials indicate that Folicur can suppress, but does not eliminate, scab disease and the accumulation of the mycotoxon deoxynivalenol (DON) in wheat. Application timing at flowering is critical for effective use of Folicur to manage scab. A prediction system based on rainfall, temperature, humidity, and previous crop was developed at Pennsylvania State University and Ohio State University for predicting the likelihood of scab in wheat and proper timing for fungicicide applications (www.wheatscab.psu.edu/). This system was just put into place in Illinois in 2004.

The prediction system and Folicur together with moderately resistant or resistant varieties provide producers with new tools for management of wheat scab. Similar approaches may be also useful for improved management of other diseases in the future.

Symptoms of head scab with portions of wheat heads bleached prematurely

"Symptoms of head scab with portions of wheat heads bleached prematurely”.

Sample output from the Wheat Fusarium Head Blight Prediction Center

“Sample output from the Wheat Fusarium Head Blight Prediction Center (www.wheatscab.psu.edu) based on a flowering date of May 13, 2004. The red and yellow colors represent areas with high and medium risk of scab development for wheat that was flowering on that date.”

Department of Crop Sciences
College of Agriculture, Consumer and Environmental Sciences
University of Illinois Extension
Copyright © 2004 University of Illinois
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