After visiting with Mary Burrows (MSU Disease Diagnostician), we are estimating that stripe rust will begin injuring cereal grains this week. Below are a few notes I have compiled on biology and management of the stripe rust fungus.
• Fungal spores attack wheat consuming the nutrients synthesized by the host plant.
• Spread by green bridge and wind dispersal. Community disease like WSMV with multiple infection cycles.
• Spores on the ground are dead because they need living plant tissue to survive. Spores will over-winter on volunteer plants. Wet weather in the fall will promote stripe rust survival.
• Do not spray fungicides past the flowering stage.
• Check labels to make sure you don’t exceed the amount of fungicide you can apply to a crop in a single year (tilt= 8 ounces per year).
• Post-harvest interval on fungicides (you cannot harvest until 30 days have passed after spraying).
• Fungicides last 10-14 days after application as a general rule (Burrows, 2013).
• Fungicides protect the tissue they are sprayed on. If the flag leaf emerges after spraying it will not be protected. Spraying after flag leaf is recommended for non-resistant varieties.
• Resistant varieties may not need to be sprayed because they can be resistant to infection. Resistant winter wheat varieties include Colter, Judee, Loma, Northern, SY Clearstone 2CL, Warhorse and Yellowstone. Resistant spring wheat varieties are Egan, Volt and WB-Rockland.
• Resistant plants will wall off the fungus and prevent the fungus from spreading. White, grey, or brown stripes will form as evidence of adult plant resistance.
• Resistant varieties are resistant to all 40 strains of stripe rust. If Tan spot or septoria are diagnosed in resistant varieties, the field will need to be sprayed.
If stripe rust arrives after the second joint is formed, resistant plants will remain resistant. If it arrives before second joint, the wheat will need to be sprayed as soon as possible.
The later stripe rust infests, the less damaging the rust will be to yield. Resistance will kick in after jointing when average night temperatures remain above 50 and day temperatures are between 77 and 86°F (Mary Burrows 10/13/14).
• Barley is not susceptible to the same stripe rust as wheat. If wheat next door is heavily infested, barley may be infested with a few pustules, but it doesn’t spread well in barley.
• Applying fungicide with nitrogen is risky because of crop burn.
For further information on stripe rust or other crop diseases, please contact the Chouteau County Extension office at 622-3751, or stop in for a visit. We are located in the green building next to the courthouse.
Montana State University U.S. Department of Agriculture and Montana Counties Cooperating. MSU Extension is an equal opportunity/affirmative action provider of educational outreach.
