Stripe Rust

1. Stripe Rust • Caused by Puccinia striiformis • Host is primarily wheat • Barley and some perennial grasses may be infected

2. Stripe rust vs. other foliar diseases Stem rust Tan spot Cephalosporium stripe

3. Yellowstone Promontory Johnston & Grey, 2006 Stripe Rust Stripe rust Stem rust Leaf rust

5. Susceptible Resistant

6. 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)

7. Influence of fungicide application on susceptible SW variety, McNeal Quilt, Bozeman 2007, P = 0.50

8. Stripe rust history in the United States and Montana • Discovered in 1915 by a Danish scientist visiting AZ • Found in herbarium specimens from WA in 1892 • Probably on native grasses since humans crossed into North America • Epidemics diminished 1930s until 1950s • Increased wheat production • New cultivar, Lerma Rojo, in Mexico that was highly susceptible Line. 2002. Annu. Rev. Phytopathol. 40:75-118

9. History, cont’d • 1960-1967 severe epidemics • Variety Omar very susceptible, widely planted • Sharp and Hehn (1963); stripe rust is probably endemic in Gallatin Valley and Flathead Lake area • Army and USDA funded research as potential biological weapon in the Cold War; impact on national security • Nugaines released in 1965, major cultivar planted until 1981, durable resistance for 40 years • 1968-2000s, not a major pathogen, focus shifted to breeding resistance to stem and leaf rusts • Also, weather not as conducive for epidemics Line. 2002. Annu. Rev. Phytopathol. 40:75-118

10. Stripe rust history • First described in 1777 in Europe • Became a problem in MT early 1900s • 2003: WA 25% yield loss • Favorable weather and new races • Survived winter in MT • New strains can grow when temperatures are warmer

11. X Stripe rust pathogen • Can travel on wind from other wheat-producing regions • Survives on both winter and spring wheat (living tissue) • GREEN BRIDGE • Not as common in the western region because there is less winter wheat • Favored by cool, wet conditions • Barley is susceptible, but it may escape infection due to early maturity

12. Stripe rust pathogen New isolates grow faster at higher temperatures + New isolates have significantly lower latent periods at 18C than 12 C (64F/54F) =Stripe rust caused by new isolates tends to develop faster at relatively high temperatures

13. Yellowstone Promontory Johnston & Grey, 2006 Stripe rust pathogenPST-102

14. X Stripe rust pathogen • Survives on both winter and spring wheat (living tissue) • GREEN BRIDGE • Favored by cool, wet conditions • Barley is susceptible, but it may escape infection due to early maturity

15. Stripe rust control • Eliminate green bridge • Use resistant varieties • plantsciences.montana.edu/crops • If you don’t plant a resistant variety, you may need to apply fungicide – need 4-5 bu yield gain to pay for the application cost • If stripe rust is present: Spray between the period of stem elongation and heading – need to protect the flag leaf. Check the preharvest interval on the fungicide label

16. Stripe rust variety evaluation: Winter wheat Kalispell and Bozeman 2006 • Resistant: Bighorn, Jagalene, NuFrontier, NuHorizon, Quantum, Promontory, Rampart, Yellowstone • Moderately resistant: Jerry, Ledger, Pryor • Susceptible: CDC Falcon, Genou, Rocky • Very susceptible: Above, BigSky, Morgan, Neeley, NuSky, NuWest, Paul

17. Stripe rust variety evaluation: Winter wheat Bozeman, 2006 Grey, 2006

18. Grey, 2006

19. Grey, 2006

20. Stripe rust variety evaluation: Spring wheatHuntley, 2005 • Resistant: Conan, Freyr, Buck Pronto, Alsen, Choteau • Moderately resistant: Agawam, Reeder, Fortuna, Scholar, Explorer • Susceptible: Knudson, Outlook, Hank, Ernest • Very susceptible: NorPro, McNeal

21. Fungicides for stripe rust Quilt, 14 fl oz/a • Contact fungicides such as Bravo are not effective • Tilt is marginally effective • Tilt, Quadris, Stratego, Headline and Quilt are registered for stripe rust control on wheat and barley

22. Fungicides increase yield and test weight in stripe rust susceptible varieties under stripe rust pressure (Bozeman, 2006)

23. Fungicides increase yield and test weight in stripe rust susceptible varieties under stripe rust pressure (Bozeman, 2006) Grey, 2006

24. Even ¼ rate fungicide at flag leaf stage can improve yield under stripe rust pressure (Bozeman 2006)

25. Influence of fungicide application on 2 stripe-rust infected WW varieties Big Sky (Susceptible) Yellowstone (Resistant) 13 June 1 June 18 June Quilt, 14oz, Bozeman 15 June, 2007; P < 0.004, LSD = 28 Stripe rust first confirmed Bozeman 31 May, 2007

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. Future: Stripe rust outlook • Stripe rust inoculum may be available on winter wheat next spring – scout your fields; check AgAlerts • Weather dependent • Mild winter • Cool, wet spring • Scout and apply fungicide early

28. Stripe rust control • Eliminate green bridge • Use resistant varieties • plantsciences.montana.edu/crops • If you don’t plant a resistant variety, you may need to apply fungicide – need 4-5 bu yield gain to pay for the application cost • If stripe rust is present: Spray between the period of stem elongation and heading – need to protect the flag leaf. Check the preharvest interval on the fungicide label