What is in this article?:
- Kentucky wheat disease discovery cause for concern across Southeast
- Probably not isolated find
•UK soil scientist Lloyd Murdock found wheat blast on a single wheat head May 18, 2011 at a UK Research and Education Center research plot in Princeton.
• Wheat blast is a disease that is recognized as an emerging threat worldwide.
• Crop losses of 40 percent are common and cases of 100 percent loss have been reported.
WHEAT BLAST on the head of wheat found in Kentucky
Probably not isolated find
With Farman’s research linking the wheat blast found in Kentucky to annual ryegrass, it’s very unlikely this is an isolated find.
“It’s very unlikely we’re the only ones who have it,” said Don Hershman, UK Extension plant pathologist. “Annual ryegrass is a very common forage crop in states to our south.”
UK researchers suspect it may have been misdiagnosed in the past as Fusarium head blight, a very common disease with very similar symptoms to wheat blast.
However, there are some distinct differences between the two diseases. Wheat blast will appear in fields slightly earlier than Fusarium head blight.
In addition, Fusarium head blight tends to give infected glumes and kernels a salmon to pinkish tint, and the disease is often found sporadically throughout affected heads.
Wheat blast, like Fusarium head blight, results in partial death of diseased heads but does not cause multiple infected areas within single heads. With blast, heads will turn white or tan from the point of infection upward and have what looks like grayish mold growing at the point of attachment of individual spikelets that make up the wheat head.
If producers see what looks to be Fusarium head blight, but symptoms appear earlier than expected, and they do not see evidence of salmon or pinkish discoloration in diseased tissue, there is a good chance it is wheat blast, said UK specialists.
The fungus that causes wheat blast thrives in warm, wet conditions. This is believed to be the reason why wheat blast in Kentucky is not currently a production problem, even though the causal fungus has apparently been around for years. The weather is simply not favorable for blast development during a normal Kentucky spring.
Farman said he usually looks for the disease on ryegrasses and other host plants in July and August.
Finding the fungus infecting wheat in late May 2011 was highly unusual, but could indicate that wheat blast and related diseases in ryegrasses might become more problematic if average spring temperatures trend warmer in future years, especially if accompanied by increased moisture.
Although UK specialists do not believe wheat blast represents a current economical threat to Kentucky’s wheat crop, they do believe it is important to get a better feel for how common the disease is in Kentucky.
They are encouraging producers to scout wheat fields for blast, as well as observe annual and perennial ryegrasses for the occurrence of gray leaf spot lesions on leaves.
“Gray leaf spot first appears as dead lesions that are elliptical or roughly diamond-shaped and range in color from gray to tan with a thin, brown border,” said UK Extension plant pathologist Paul Vincelli. These lesions can quickly turn into leaf blight which causes the leaf to completely dry up.
If producers suspect they have wheat blast or gray leaf spot, they should send a sample to the UK Plant Disease Diagnostic laboratories in Princeton or Lexington.
Farman added it’s fortunate that researchers found the disease at such a low level, as it provides an early warning of a possible emerging issue and, hopefully, will give researchers time to develop resistant varieties for combating the disease before it becomes a major threat to wheat production.
Farman is working with the International Wheat Blast Consortium led by researchers at Kansas State University. The group is trying to identify wheat varieties that are resistant to wheat blast and characterize the wheat blast pathogen using molecular markers.
(Already in January of this year, Kentucky wheat growers were being warned about possible disease problems because of the mild winter. You can read what the experts were saying about leaf and stripe rust at that time by visiting http://southeastfarmpress.com/grains/mild-winter-could-help-spread-wheat-diseases. And as wheat grows in popularity in the Southeast there has been a trend towards wheat following wheat in cropping patterns. For a discussion of that and some of the problems tha may occur, see http://southeastfarmpress.com/grains/beware-pest-problems-wheat-following-wheat-0).