May 1, 2008 

 

Winter wheat crop in US state of Kansas threatened by disease

 

 

The Kansas winter wheat crop faces an increased risk for significant yield loss due to disease pressure, plant pathologists said.

 

The Kansas Wheat Commission and Kansas Association of Wheat Growers issued an alert that said the threat from leaf rust and powdery mildew has increased "dramatically" in the last week.

 

The issue is of particular concern as leaf rust was "very severe" last year, Bill Bockus, a plant pathology professor at Kansas State University, told Dow Jones Newswires.

 

"The current presence of even low levels of leaf rust and severe powdery mildew suggests that potential for yield loss is significant," the alert said. "Yield losses of greater than 35 percent can be expected if the leaf rust and powdery mildew move onto the flag leaves of susceptible varieties prior to flowering. Varieties that are resistant to leaf rust will not have this much yield loss from leaf rust, but may still be vulnerable to powdery mildew or other diseases."

 

Leaf rust was discovered last week in commercial fields and variety demonstration plots in south-central Kansas, affecting both Jagger and Jagalene wheat, two of the states top three planted varieties.

 

Leaf rust was observed in trace levels on Overley near Stillwater in the neighbouring state of Oklaloma, the alert said. The alert warned growers that they may soon see disease cases in Overley, the remaining of the three most popular wheat variety not affected by disease so far.   

 

The region's recent weather conditions have been "simply perfect" for leaf rust to spread, with windy days followed by light showers and dews through the night, according to a report from Bob Hunger, an extension wheat pathologist and professor of plant pathology at Okalahoma State University.

 

However, expanded fungicide spraying should help minimize damage.

 

Growers are expected to increase fungicide sprayings on the crop this year due to strong wheat prices, Bockus said. That may help lessen the impact of disease pressure.

 

"In previous years, fungicides were not very popular," he said. "Probably less than 1 percent of the acres was sprayed because of the cost. Now that wheat is US$8 to US$10 a bushel, it makes it much more possible,"  

Stripe rust, which is even more aggressive than leaf rust, is not very prevalent so far in Kansas, Bockus said. That is "one bright spot" for the crop, he said.