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Stripe Rust in Winter Wheat

 

Stripe Rust in Winter Wheat

Disease Facts

  • Stripe rust is caused by the fungus Puccinia striiformis.
  • Stripe rust does not typically overwinter in Canada and the northern U.S., it travels on air currents from the southern U.S.
  • It affects the leaf and head of wheat.
  • The lesion colour (pustule) is yellow and stripe shaped.
  • Is favoured by cooler temperatures from 10⁰ to 15⁰ C (50⁰ to 60⁰ F).

Disease Symptoms

  • Yellow coloured pustules form in stripes on the leaves, often looking like stitches from a sewing machine.

    Yellow coloured pustules form in stripes on wheat leaves, often looking like stitches from a sewing machine.

Disease Life Cycle

  • Stripe rust takes 10 to 14 days to cycle, meaning under ideal conditions, a spore landing on a leaf and infecting the leaf can produce a lesion that spreads new spores in 10 to 14 days.
  • Ideal temperatures are 10⁰ to 15⁰ C (50⁰ to 60⁰ F); at temperatures below 5⁰ C (40⁰ F) the fungus cannot produce new spores, and at temperatures above 29⁰ C (84⁰ F) the pathogen will die.
  • Remember, the most critical leaf to protect is the flag leaf. Unless disease pressure is so high that tillers are being killed, the plant can tolerate infection without much yield loss.
  • In the case of highly susceptible varieties if flag leaf lesions are observed on most plants spraying is warranted as defoliation can occur rapidly.

We Saw It in 2016; Why Again in 2017?

  • Another warmer than usual winter likely had the greatest impact for what we are seeing in fields.
  • Adequate moisture in the Southern U.S. and a milder winter allowed stripe rust to overwinter further north, thus allowing for a more rapid build-up of inoculum this spring.
  • The mild winter also allowed for better leaf survival of seedling wheat leaves providing greater leaf surface area for inoculum to be produced on.

    Pioneer® brand wheat seed bags

Scouting Practices

  • Scout your fields and note the severity across the whole field.  It is important to understand the scope of the infection, weather forecast and variety susceptibility before making a decision on whether or not to spray.

Variety Differences

  • There are significant differences in susceptibility to stripe rust in the Pioneer® brand wheat line up. See chart below. In the Pioneer lineup, only Pioneer variety 25R46 is below average.

    Wheat stripe rust scores for 5 Pioneer® brand varieties.

    NUMERIC RATINGS: 9 = Excellent; 1 = Poor

Disease Management

  • Ontario researchers recommend that only triazole fungicides (e.g. Caramba®, Folicur®, Tilt®, Prosaro®) be used at the boot stage or later because of increased risk of high DON levels with the use of a strobilurin (e.g. DuPont™ Acapela®, Quadris®).
  • Many fungicides provide excellent control of stripe rust, please read and follow label directions for rates, timing and coverage recommendations.
  • Depending on how the disease progresses, in 2017 fungicide timing for head blight may also be well timed for stripe rust.

Conclusion

  • Stripe rust thrives in cooler temperatures, warmer temperatures will decrease infection potential and spore production.
  • Many fungicides can be used to control stripe rust, be sure to follow label directions.

 

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The foregoing is provided for informational use only. Please contact your authorized Pioneer sales professional for information and suggestions specific to your operation. Product performance is variable and depends on many factors such as moisture and heat stress, soil type, management practices and environmental stress as well as disease and pest pressures. Individual results may vary.

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