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Wheat Tan Spot Increases Through Canada

25 July 2012

CANADA - Cereal leaf spot diseases have become prevalent across southern and central Alberta. Tan spot on wheat is increasing throughout the south, but severely infected fields are rare.

Other diseases on wheat include Septoria, Stagonospora and some powdery mildew; however, most of the symptoms remain on lower leaves. On barley, diseases such as scald, net blotch and spot blotch can be commonly found.

“When cereal leaf spot diseases appear on lower leaves it is important to remember that fungicide applications will only provide a yield benefit and economic return when they are staged to protect the upper two or three leaves in the canopy,” says Michael Harding, research scientist, plant pathology with Alberta Agriculture and Rural Development.

“In wheat, it is important to protect the flag and penultimate (flag minus1) leaves. For barley, protection of the three upper leaves will minimize yield loss. Fungicides applied too early (prior to the beginning of flag leaf emergence), or too late (after extensive disease onset in the upper canopy), are unlikely to provide protection where and when needed, and therefore will be unlikely to have economic benefit.”

As many cereal crops in southern Alberta have headed, or are beginning to head, it is also important to consider a fungicide application for protection against Fusarium Head Blight (FHB) in areas where the disease is commonly found. Successful fungicide timing to suppress FHB in wheat must fall within the 7- to 10-day window during anthesis. In barley, fungicide is applied just before, or near, the time of full head emergence. Fungicide applications will act preventatively to suppress disease, but will not cure infections after disease onset.

Scout and evaluate disease situations in cereal fields regularly, and be ready to spray when risk thresholds are reached,” says Professor Harding. “Read product labels carefully to ensure proper rates, methods and staging for fungicide applications.”

Consult the Crop Protection guide for information on registered fungicides and label information. The guide is available by clicking here.

TheCropSite News Desk

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