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The stripe rust epidemic of 2011: why? and what next?

The stripe rust epidemic of 2011: why? and what next?. Dr. Mary Burrows Montana State University Bozeman, MT. Why was stripe rust so bad this year?. Widespread fall infection Extended fall Deep, lengthy snow cover Favorable spring temperatures

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The stripe rust epidemic of 2011: why? and what next?

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  1. The stripe rust epidemic of 2011: why? and what next? Dr. Mary Burrows Montana State University Bozeman, MT

  2. Why was stripe rust so bad this year? • Widespread fall infection • Extended fall • Deep, lengthy snow cover • Favorable spring temperatures • Flooding created wet, humid conditions throughout the year • Even after day temps became hot, night temps were favorable for infection (50-70F) • A widely planted, susceptible variety (Genou) • New strains • April: alerts from Xianming Chen that stripe rust was off to an ‘early start’ in WA

  3. Fall infection by stripe rust, 2010

  4. Fall 2010: Distribution of stripe rust

  5. Reports of stripe rust in Montana 20 June, 2011(Diagnostic lab samples)

  6. Stripe rust spore cloud: 23 June, 2011 near Kremlin (Hill Co.) Photo courtesy of Ryan McCormick

  7. Degree day map, 9 May, 2011First reports from Ronan, Kalispell

  8. Degree day map, 24 May, 2011Reports from Havre, Fort Benton, Great FallsMary: “Genou is what??? Send a sample”

  9. June 1: “Dan/Jeannie (Pondera, Toole Co) – it’s coming your way”

  10. June 10: Pondera Co’s 1st sample came into the office

  11. Why didn’t the epidemic stop when it got hot? • Stripe rust disease progress is tied to night time temperatures 50 to 70°F Great Falls 1 May to 30 July

  12. The rusts of wheat Stripe Stem Leaf Jim Berg, MSU Yellow Black Red

  13. Rust diseases are not mutually exclusive

  14. Stripe rust: gen’l WA or Canada Leaf rust, stem rust: ‘Puccinia pathway’

  15. Normally, this is wheat

  16. Great Falls area, 23 June, 2011 WW Variety: Genou

  17. Yellowstone Promontory Johnston & Grey, 2006 Stripe Rust: variety resistance is very effective at reducing yield losses Susceptible variety Resistant variety

  18. CDC Falcon Yellowstone

  19. Yellowstone Promontory Johnston & Grey, 2006 Stripe Rust: variety resistance is very effective at reducing yield losses Susceptible variety Resistant variety

  20. Seedling infection vs. adults • Seedling infections are often not in ‘stripes’ • Yellow rust • Seedling infections tend to be strain – specific (single genes) – easily overcome by the pathogen • Adult resistance is non-race specific, more durable • Seedling and adult plant responses can be different • HTAP resistance: High Temperature, Adult Plant resistance – doesn’t kick in until after stem elongation (Feekes 4-9; Zadocks 30-39) and average night temperatures remain above 50 and day temps are between 77 and 86 F

  21. Current classifications: Winter Wheathttp://plantsciences.montana.edu/Crops/2011data/2011WinterWheatVarieties.pdfTables 3, 4, and 14

  22. Current classifications: Spring wheathttp://plantsciences.montana.edu/Crops/2011data/2011WinterWheatVarieties.pdfPages 23 and 24 Note: this needs to be updated with 2011 data

  23. Xiangming Chen, WSU, 2010Stripe rust would have caused 54% yield loss in WA without fungicide application in 2010 if all varieties were as susceptible as PS279If all resistant cultivars were grown, 1% yield loss with no fungicide application Resistant check Susceptible check

  24. Fungicides Ron Muzzana, 2011

  25. Note: these are generalizations about fungicide classes

  26. Influence of fungicide application on two stripe-rust infected WW varieties Yellowstone (Resistant) c c c c Big Sky (Susceptible) b b b a (Quilt, 14oz, Bozeman 2007; P < 0.001, LSD = 6.3)

  27. On-farm/on-station fungicide trials: flag applications (sprayed 9-10 June, rated 7-8 July) Sprayed too early for max SR

  28. Stripe rust on WWBozeman, 2011 – Bynum (Resistant to stripe rust) Sprayed 5 June, Feekes 5, 2011

  29. Bynum Winter Wheat: ResistantNo yield benefit to tillering or flag fungicide application(Priaxor, Headline, Evito, Quilt Xcel, Twinline study, Bozeman, 2011) Photo: M. Moffet

  30. Stripe rust on SWBozeman, 2011 – Vida – MR to stripe rust

  31. Glume infection of stripe rust

  32. ‘Rescue’ spraying? Hunger and Jackson. Foliar fungicides and wheat production in Oklahoma. http://lubbock.tamu.edu/wheat/pdfs/osufoliarfunghandout04.pdf Remember your PHI!

  33. Economic impact? • Montana growers spent ~$15 mil. on fungicide • Fungicides saved growers ~$30 mil. • Yield losses cost growers ~$48 mil. • Not spraying resistant varieties saved ~$12 million Source: estimates from a grower survey, October 2011 (Burrows)

  34. What does ‘strain’ mean when talking about stripe rust? • Stripe rust is characterized by the pathogenic reaction on a series of wheat lines called ‘differentials’ • Virulence patterns have changed Stem rust differentials

  35. New strains are more aggressiveMoon and Milus, 2011 • “Even though there was more initial inoculum of isolate AR90-01 [‘old,’ PST-3], isolate AR03-33 [‘new,’ PST-78] caused significantly more disease around the transplants in the spring at both Fayetteville and Kibler”

  36. New strains infect plants at higher temperaturesMilus, E. A., Seyran, E., and McNew, R. 2006. Aggressiveness of Pucciniastriiformis f. sp.tritici isolates in the south-central United States. Plant Dis. 90:847-852. • At 54°F, old and new isolates had similar latent periods and spore germination percentages. • However, at 64ºF, new isolates averaged 2 days less for latent period and double the spore germination compared with old isolates. • Therefore, the new isolates are better adapted and, thus, more aggressive at warmer temperatures than the old isolates.

  37. A number of new strains were characterized after a severe epidemic in 2000Chen, X. M., Moore, M., Milus, E. A., Long, D. L., Line, R. F., Marshall, D., and Jackson, L. 2002. Wheat stripe rust epidemics and races of Pucciniastriiformisf. sp. triticiin the United States in 2000. Plant Dis. 86:39-46.

  38. Chen, X. M., Moore, M., Milus, E. A., Long, D. L., Line, R. F., Marshall, D., and Jackson, L. 2002. Wheat stripe rust epidemics and races of Pucciniastriiformisf. sp. triticiin the United States in 2000. Plant Dis. 86:39-46.

  39. Aecia on barberry How do new strains originate? Uredinia on Kentucky bluegrass Pycnidia on barberry Aecia on barberry Uredinia on wheat Jin, Szabo and Carson, Plant Dis., 2010

  40. What qualifies as excitement for a plant pathologist:

  41. 2010 Stripe rust strains (PSTv-#) 14 38 16,14 14, 44 22,39 46

  42. 2011 Stripe rust strains (PSTv-#) Data updated 9 Dec, 2011 14 11,14 11 17 14 11 37 14 14,37 14,37

  43. So what do those numbers mean? Virulence on differential lines of wheat

  44. What’s next? • PSTv-4 and PSTv-17 are virulent against differential line Sp (“Spalding Prolific, Yr-SP) • YrSP virulence is in low frequency worldwide • Last year Yr-SP virulent races were detected in low frequency and in 2011 increased significantly • PSTv-4 is currently in Washington, Oregon, Utah and Idaho (not MT); PSTv-17 is in MT • Bottom line: races are changing very fast; variety reactions will change, also: Scout crops, recognize the reaction types and manage appropriately

  45. Yellowstone Promontory Johnston & Grey, 2006 Stripe Rust: variety resistance is very effective at reducing yield losses Susceptible variety Resistant variety

  46. So, what about next year? • Dry fall! • Hot spots due to prevented planting; WW seeded very early • Plant a resistant variety • Use a seed treatment • Fall fungicide is generally not economical • Plan on a full rate of fungicide when spraying weeds at tillering (blends preferred) on susceptible varieties if the weather is favorable for disease development • Although stripe rust got all the glory, a lot of yield losses were due to root and crown rots • Community disease

  47. Diagnostic lab: routine functions and agricultural biosecurity • Process approximately 2000 samples/yr (~80% homeowner/horticulture) • Free to you • 100% grant funded staff, supplies, travel • Space and utilities provided by MSU • Sample submission is important • Good sample = good answer

  48. Network Responsibilities • Data collection (detectors/diagnosticians) • Communications system • Information storage and management • Data analysis • New events and analysis of new appearance • Pattern recognition • Unusual patterns of endemic problems • GIS • Event propagation • Tracking • Reporting and alerts • Link to State Departments of Ag and US regulatory • agencies

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