"If the disease comes in early and the epidemic is bad enough, you can have a significant loss of yield, especially in highly susceptible varieties," said Dr. Scott Monfort, plant pathologist with the University of Arkansas Cooperative Extension Service. The stripe rust was found by county extension agents, Monfort and others.

"We were surveying wheat fields for it because we received information that it had been found in Louisiana," Monfort said. He said they found the disease in Monroe, Arkansas, Prairie, Lee, Chicot, Ashley and Lafayette counties.

"It was found in small, localized areas with only a few plants showing symptoms," he said. "But," he added, "the disease can quickly explode on producers." "We've got probably 70,000 acres of wheat in Arkansas County," said Ken Adams, extension county agent. He said a small amount of the disease was found near Casscoe in northern Arkansas County. "We've had good weather for it to develop." Adams said he was alerting his farmers that the disease had been found and telling them that if they are growing varieties that are susceptible to the disease, they need to be monitoring their fields. He said the county office has a list of susceptible varieties.

The current weather conditions are near ideal for the disease to thrive.

The most favorable conditions for wheat stripe rust are cool temperatures, from 40 to 60 degrees, with sunny, windy days and clear, calm nights favoring long periods of dew on leaves. Moisture from dew and rain promotes germination and infection. "Once night temperatures get above 60 degrees and stays above it, then the disease potential decreases," Monfort said. "It's a cool season disease that is typical of this time of year." He said a single infection can start several cycles of spore production and produce a visible "hot spot." Heavily diseased areas can appear yellow from a distance.

"Spores from hot spots spread downwind quickly to other portions of the field and to other fields," Monfort said.

"In fields where you're seeing stripe rust, we recommend applying a fungicide after Growth State 8 (flag leaf emergence) and when you reach a threshold of one pustule per 20 leaves. However, in fields where you're seeing hot spots develop we recommend applying a fungicide immediately at, or before GS 8. The flag leaf is what we need to protect."

With stripe rust, applying a fungicide too soon is always better than applying it too late, the plant pathologist said.

"In Arkansas, we recommend that farmers not plant wheat varieties that are very susceptible to stripe rust," Monfort said. "These varieties often require two fungicide applications to adequately control the disease."

He said farmers may be so interested in yield potential of a variety that they forget about the importance of that variety's disease package, "especially if they haven't had a problem in couple of years."

The University of Arkansas has conducted research showing that an application of propiconazole fungicide or a mixture of propiconazole and strobulrin fungicides has performed well under heavy stripe rust pressure on very susceptible varieties, Monfort noted.

These fungicides vary in the amount of propiconazole they contain, so be sure to read and understand the labels and special requirements for use.

Check with your county extension agent for the MP154 publication or other wheat fungicide information. You can also go to www.uaex.edu and select Agriculture, wheat and Newsletters and Publications. The Cooperative Extension Service is part of the U of A Division of Agriculture.

B

8

3/26/07

5 Star OK

Date: 3/22/07

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