Friday, May 1, 2009

Scouting Fields one Key to Managing Wheat Foliar Diseases

By David Burton
University Extension

There are foliar diseases that can cause yield loss in winter wheat according to Jay Chism, an agronomy specialist with University of Missouri Extension in Barton County.

“The key is to apply fungicides to wheat at the early boot stage to head emergence. Research shows fungicides at this growth stage, when the flag leaf is in danger of infection will provide the most benefit,” said Chism.

According to Laura Sweets, a plant pathologist at the University of Missouri, leaf rust, strip rust and Septoria leaf blight are diseases that are likely to cause yield loss.

“The incidence and severity of these foliage diseases will depend on the weather conditions during the growing season,” said Sweets. “Susceptibility of the variety to each of these diseases and the amount of inoculum in each field will also determine the severity of disease infection.”

Most wheat foliage diseases are favored by warm, wet conditions. Frequent light rains, heavy dews, high relative humidity and warm temperatures are ideal for the buildup of foliage diseases.

So far this season in Barton County, Chism says he has seen only low Septoria pressure, while powedery mildew is beginning to develop in the thicker field canopies.

“It is important to scout wheat fields for diseases,” said Chism. “And growers should also know the difference between viral and fungal diseases.”

Fungicides will have no effect on viral diseases.

“If fungal diseases are threatening to infect the flag leaf, then applying foliar fungicides is a good practice, but farmers need to identify the disease and the severity before they make that determination,” said Chism.

Delaying fungicide applications to coincide with insecticide applications may make economic sense.

“Commodity prices are not as favorable as last year. Delaying an application of fungicides until an aphid threshold is reached may work in some instances,” said Chism.

Always be sure to follow the label recommendations when deciding to apply pesticides.

For 2009 wheat fungicide label information go to http://extension.missouri.edu/barton for products registered in Missouri.

For more information on applying foliar fungicides to wheat contact Chism at (417) 682-3579.

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