Wednesday, April 25, 2012

Kentucky: Farmers Urged to Scout for Wheat Blast

AgFax.Com - Your Online Ag News Source


University of Kentucky College of Agriculture specialists are encouraging Kentucky wheat producers and crop consultants to scout their fields for a new disease that could have important implications for future crop years.

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. No additional instances of the disease were found even after extensive scouting of the involved research plots and neighboring fields by UK researchers. It is likely, however, that additional infected heads existed but at levels too low to make detection possible.

Wheat blast is a disease that is recognized as an emerging threat worldwide. Caused by the fungus Magnaporthe oryzae/Pyricularia grisea, the disease was first detected in southern Brazil in 1985 and has since become a problem in several of its neighboring countries. Crop losses of 40 percent are common and cases of 100 percent loss have been reported. Currently, there are no commercially available resistant varieties and fungicidal programs targeting wheat blast have generally been ineffective.

The Kentucky find is the first known occurrence of wheat blast outside of South America. However, a related pathogen has caused a disease called gray leaf spot on annual ryegrass in Louisiana and Mississippi since the 1970s and on perennial ryegrass in much of the humid regions of the United States since 1992. Annual ryegrass is a common forage crop in the South, and it is also recognized as a weed in Kentucky wheat fields. Perennial ryegrass is grown as a turfgrass in Kentucky, as well as an infrequent forage grass.

There is also a disease common in rice produced in the Mid-South called rice blast. Although rice blast is caused by the same fungus, isolates of the fungus known to infect rice do not infect wheat and vice-versa. Thus, rice producers who grow wheat in extreme southwest Kentucky and surrounding states are not at increased risk from the wheat blast fungus.

UK plant pathologist Mark Farman has spent most of his career studyingthe fungi that cause the blast and gray leaf spot diseases. He sequenced the genome of the isolate found at the UK Research and Education Center and compared it to the genetic structure of isolates found on ryegrasses and from South American wheat blast.

Farman found the annual ryegrass pathogen and the wheat blast pathogen discovered at the Research and Education Center to be genetically very similar. This led him to think that the annual ryegrass pathogen gained the genetic ability to infect wheat. The UK wheat blast pathogen’s genetic structure was most different from the wheat blast pathogen known to affect South American wheat. His results, thus far, suggest that the blast fungus found on the Kentucky wheat head has probably been around for at least a decade or longer on annual and perennial ryegrass and perhaps on wheat, and almost certainly was not imported with grain originating from South America.




This is important, because it means that the new find is not an exotic pathogen. Farman said the pathogen is usually host-specific, meaning the fungus that attacks annual ryegrass normally will only attack annual ryegrass or its close relative, perennial ryegrass. This is the first time he’s seen this pathogen able to “jump” hosts.

Samples of the fungus collected from Kentucky wheat were also sent for testing to Gary Peterson, a researcher with the U.S. Department of Agriculture’s Agriculture Research Service. He confirmed the fungus collected from wheat found in Princeton was able to infect wheat. Moreover, he found the Kentucky isolate was similar in its ability to cause disease as isolates that cause wheat blast in South America.

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 that 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 that 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.


Tags: , , ,


Leave a Reply

Name and Email Address are required fields. Your email will not be published or shared with third parties.

Sunbelt Ag News

    AFB Grain-Soybean Close: Prices Move Mostly Higher8-28

    AFB Cotton Close: Market Turns Lower8-28

    AFB Rice Close: Futures Lower Across the Board8-28

    Grain TV: Ukraine Conflict Escalates, Boosts Wheat8-28

    DTN Livestock Close: Cattle Futures Slam Sharply Higher8-28

    Doane Cotton Close: News from China Moves Market Lower8-28

    Alabama: Pesticide Clean Days, Sept. 3-48-28

    Oklahoma: Fall Cotton Tour, Hydro, Sept. 118-28

    Rice Harvest Eases Into Gear In Midsouth – AgFax8-28

    Ag Drones Under Scrutiny: Farmers Impatiently Await FAA Rulings – DTN8-28

    USDA Readies Dairy Program, Producers Able to Sign Up Tuesday – DTN8-28

    AgFax Rice Review: China Could Be Big U.S. Market; Drip Irrigation Good for Yields, Environment8-28

    DTN Cotton Close: Settles at 3 Session Low8-28

    DTN Grain Close: Wheat Higher As Russia Expands Military Presence8-28

    DTN Livestock Midday: Strong Gains Develop in Cattle Futures8-28

    U.S. Grain Transportation: Inspections Continue to Increase8-28

    Farm Program Decisions Hinge on Uncertain 2014 Crop Prices8-28

    Raindrops Keep Falling on Heads of Many Midwest Farmers — DTN8-28

    DTN Grain Midday: Wheat Leads Markets Higher8-28

    Economist: Big Potential in China for U.S. Corn, Livestock Exports8-28

    John Deere Lays Off 460 from Waterloo, Iowa Factory8-28

    DTN Cotton Open: Slides Even after Supportive Sales8-28

    U.S. Energy: Retail Gas Prices Follow Crude Prices Lower8-28

    Gasoline Prices: Decline by 2 Cents8-28

    Propane Stocks: Up to 74.7M Barrels8-28

    Diesel Prices: Average Drops a Penny8-28

    DTN Livestock Open: Futures to Open Under Selling Pressure8-28

    DTN Grain Open: Wheat Higher On Russian Aggression8-28

    Keith Good: Map Controversy Puts EPA on Defensive about Water Rule8-28

    Sugarcane Aphid In Grain Sorghum: Florida, Georgia Find Infestations8-27

    Cotton – Midsouth – Bolls Opening, Early Defoliation Nears – AgFax8-27

    Midwest Corn and Soybeans Need Warm, Clear September – AgFax8-27

    Cotton – Southeast – More Open Bolls, Lingering Pests – AgFax8-27

    Farm Groups Release Water Maps to Challenge CWA – DTN8-27

    Texas: 2 More Counties Make Natural Disaster List8-27

    Southwest May Face ‘Megadrought’ This Century, Say Scientists8-27

    China’s Citizenship Reform Should Benefit Farmers — DTN8-27

    What Can We Learn about Corn, Soybean Yields from Crop Tours?8-27

    Consider Sulfur for Your Fertility Plans This Fall — DTN8-27

    Rough Rice: Stocks Down 13 Percent from August 2013 — USDA8-27

    AgFax Peanut Review: Clemson Field Day Next Thurs; New Allergy Research Shows Promise8-27

    South Carolina: Peanut Field Day, Blackville, Sept. 48-27

    Cotton in Southwest – Early Yield Reports Good; Oklahoma Needs Rain – AgFax8-26

    Weather, Insects, Equipment Insurance, Health Issues – What Else? – DTN8-26

    DTN Fertilizer Trends: Prices Unlikely to See Significant Declines8-26

    Will High Yields Rescue 2014 Crop Returns? Not for Many.8-26

    Your Farm Business and the Affordable Care Act8-26

    AgFax Grain Review: Midwest Storage Concerns; Cereal Rye Makes Good Cover Crop8-26

    USDA: Weekly National Peanut Prices8-26

    Pork: U.S. Exports to Japan Increase but Competition is Growing — DTN8-26

    Arkansas: UA Cotton Field Day Slated Sept. 9 at Manila8-26

    Missouri: Fisher Delta Center Field Day Set Sept. 2 in Portageville8-26

    Doane Cotton Close: Finishes Down Very Slightly8-25

    Corn Rootworm Researchers Handcuffed by Time — DTN8-25

    Good on Grain: Looking for a Corn Consumption Response8-25

    DTN Fertilizer Outlook: Domestic Ammonia Prices Increase8-25

    Environmental Health: Farm-Based Nitrogen Emissions Unavoidable, Can Be Minimized8-25

    Brazil Soybeans: Prices Slide as Acreage Rises — DTN8-25

    Flint on Crops: Stress Avoidance Critical for Crops — and People8-25

    Sunbelt Ag Events

     

    About Us

    AgFax.Com covers agricultural trends and production topics, with an emphasis on news about cotton, rice, peanuts, corn, soybeans, wheat and tree crops, including almonds, pecans, walnuts and pistachios.

      

    This site also serves as the on-line presence of electronic crop and pest reports published by AgFax Media LLC (formerly Looking South Communications).

        

    Click here to subscribe to our free reports.

      

    We provide early warnings and confirmations about pests, diseases and other factors that influence yield. Our goal is to quickly provide farmers and crop advisors with information needed to make better and more profitable decisions.

         

    Our free weekly crop and pest advisories include:

    • AgFax Midsouth Cotton, covering cotton production and news in Alabama, Arkansas, Louisiana, Mississippi, Tennessee and Missouri.

    • AgFax Southeast Cotton, covering cotton production and news in Alabama, Florida, Georgia, North Carolina, South Carolina and Virginia.

    • AgFax Southwest Cotton (new for 2013!), covering cotton production and news in Texas, Oklahoma, Kansas and New Mexico.

    • AgFax West (formerly MiteFax: SJV Cotton), covering California cotton, alfalfa, tomatoes and other non-permanent crops in California's Central Valley.

    • AgFax Rice covering rice production and news in Arkansas, Louisiana, Mississippi, Missouri and Texas.

    • AgFax Peanuts, covering peanut production in Alabama, Arkansas, Florida, Georgia, Louisiana, Mississippi, North Carolina, South Carolina, Texas and Virginia.

    • AgFax Southern Grain: covering soybeans, corn, milo and small grains in Southern states.

    • AgFax Almonds, covering almonds, pistachios, walnuts and other tree crops in California's Central Valley.

    • AgCom 101, providing guidance to ag professionals involved in social media.

    Our newsletters are sponsored by the following companies: FMC Corporation Chemtura Dow AgroSciences.

          

    Mission statement:

    Make it as easy as possible for our community of readers to find and/or receive needed information.

              

    Contact Information:

    AgFax Media. LLC

    142 Westlake Drive Brandon, MS 39047

    601-992-9488 Office 601-992-3503 Fax

    Owen Taylor Debra L. Ferguson Laurie Courtney

          

    Circulation Questions?

    Contact Laurie Courtney