Leaf Rust in Winter Wheat

Over the past few weeks, I have been touring the MCVET winter cereal sites.  This week (June 16th), I found leaf rust in a winter wheat trial near Carman, Manitoba (see Figure 1).

Leaf Rust Pustule - Winter Wheat 2015 (P.de Rocquigny)

Figure 1: Leaf Rust Pustule – Winter Wheat 2015 (Photo by Pam de Rocquigny)

Wheat leaf rust, caused by Puccinia triticina, is one of the most common diseases of wheat on worldwide.  The most characteristic signs of leaf rust infection are the rusty-red spores in round to oval pustules breaking through the leaf surface.

Yield loss and reduction of test weight are related to disease severity and time of infection. Yield losses of 30 percent to 40 percent have been recorded when severe infection occurred before flowering and damage on the flag leaf was high (> 60 percent to 100 percent).  However, if severe leaf rust does not occur until dough stages of kernel development or beyond, yield losses may be in the range of 5 percent to 15 percent.

Genetic resistance in varieties to leaf rust limits infection and retards fungus growth and spore formation. The population of the leaf rust fungus is genetically diverse and made up of many races. Different races have the ability to cause infection on varieties with different resistance genes. The leaf rust pathogen is dynamic, and races are constantly changing. Varieties formerly considered resistant can become susceptible if new rust races develop. Resistant levels are reviewed (and updated if necessary) each year for varieties and are provided in SEED MANITOBA (www.seedmb.ca).

Surveys & Monitoring is Important!  Field surveys conducted during the growing season by AAFC and MAFRD is critical as it allows the sampling of the natural populations of pathogens in the field to determine the virulence in the populations.  This in turn provides an indication of the effectiveness of current resistance sources for new crop cultivars. Growers should also monitor their crops throughout the season and be aware of disease developments in their local area. Monitoring, and early detection and reporting of rust will improve disease management outcomes.

For more information on leaf rust, its symptoms, biology, and control measures , visit MAFRD’s website at http://www.gov.mb.ca/agriculture/crops/plant-diseases/leaf-rust-wheat-barley-oats.html

Submitted by:  Pam de Rocquigny, Provincial Cereal Crops Specialist, MAFRD

 

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Leaf Rust in Spring Wheat

Over the past several weeks, I have been touring the MCVET cereal sites.  Last week, I found leaf rust in one of the spring wheat trials in southern Manitoba.

Wheat leaf rust, caused by Puccinia triticina, is one of the most common diseases of wheat on worldwide.  The most characteristic signs of leaf rust infection are the rusty-red spores in round to oval pustules breaking through the leaf surface.

Leaf Rust in MCVET Spring Wheat Trial 2014

Leaf Rust in Spring Wheat. Photo by: Pam de Rocquigny, 2014

Yield loss and reduction of test weight are related to disease severity and time of infection. Yield losses of 30 percent to 40 percent have been recorded when severe infection occurred before flowering and damage on the flag leaf was high (> 60 percent to 100 percent).  However, if severe leaf rust does not occur until dough stages of kernel development or beyond, yield losses may be in the range of 5 percent to 15 percent.

Genetic resistance in varieties to leaf rust limits infection and retards fungus growth and spore formation. The population of the leaf rust fungus is genetically diverse and made up of many races. Different races have the ability to cause infection on varieties with different resistance genes. The leaf rust pathogen is dynamic, and races are constantly changing. Varieties formerly considered resistant can become susceptible if new rust races develop. Resistant levels are reviewed (and updated if necessary) each year for varieties and are provided in SEED MANITOBA (www.seedmb.ca).

Surveys & Monitoring is Important!  Field surveys conducted during the growing season by AAFC and MAFRD is critical as it allows the sampling of the natural populations of pathogens in the field to determine the virulence in the populations.  This in turn provides an indication of the effectiveness of current resistance sources for new crop cultivars. Growers should also monitor their crops throughout the season and be aware of disease developments in their local area. Monitoring, and early detection and reporting of rust will improve disease management outcomes.

Submitted by:  Pam de Rocquigny, Provincial Cereal Crops Specialist

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Happy Robigalia!

The urediniologists at the USDA-ARS Cereal Disease Laboratory sent a greeting today, April 25th,  wishing everyone Happy Robigalia!

You might wonder what Robigalia is.  Instituted by Numa Pompilius (the second king of Rome), the Robigalia, an ancient agricultural festival celebrated in honor of Robigo (or Robigus, the gender was uncertain), the goddess of blight, red rust, or mildew, was celebrated on April 25, when the crops were most vulnerable to disease.  The Robigalia was one of several agricultural festivals in April to celebrate and vitalize the growing season.

The greeting was sent to members of the Cereal Rust Survey listserv list, whose purpose is to provide a format for cereal researchers and extension personnel to share observations of cereal rusts and other cereal diseases.  For more information on the “Cereal Rust Situation Reports” and “Cereal Rust Bulletins”, visit USDA-ARS website at http://www.ars.usda.gov/main/docs.htm?docid=9757

Submitted by:  Pam de Rocquigny, MAFRD Cereal Crops Specialist

 

 

 

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Update on Cereal Rust

Submitted by:  Holly Derksen, MAFRI Field Crops Pathologist
 
Leaf rust in winter wheat was observed in the MCVET trials in Carman and Winnipeg over the last week (see image below). This is the first report of cereal rust in Manitoba this year and it has not been reported in commercial fields. Pustules were observed mostly on lower leaves and at low severity. The MCVET trials do not receive any fungicide applications.
 

Leaf Rust
Photo taken by Holly Derksen (2013)

 
Due to its late arrival this year, cereal rusts will not have an impact on yield as most crops in the province are further advanced. The latest a fungicide ever needs to be applied in wheat is at the FHB timing ie. full head emergence to early anthesis.
 
Taken from the Manitoba Insect and Disease Update for the Week of July 22, 2013:  http://www.gov.mb.ca/agriculture/crops/seasonal-reports/insect-report-archive/insect-report-2013-07-23.html
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