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

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

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

Resistant Susceptible

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

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

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 Annu. Rev. Phytopathol. 40:75-118

History, cont’d 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 s, not a major pathogen, focus shifted to breeding resistance to stem and leaf rusts –Also, weather not as conducive for epidemics Line Annu. Rev. Phytopathol. 40:75-118

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

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 X

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

Stripe rust pathogen PST-102 Yellowstone Promontory Johnston & Grey, 2006

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 X

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

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

Stripe rust variety evaluation: Winter wheat Bozeman, 2006 VarietyYield (Bu/a) % Stripe rust (June 28) Yellowstone997 Promontory939 Jerry8910 NuFrontier8510 Rampart8018 Pryor8042 Jagalene7912 CDC Falcon7855 Genou7136 Ledger7041 Neeley7072 NuSky6682 NuWest6583 Correlation = p < Grey, 2006

Stripe Rust Corr. w/ YieldCorr. w/ Test Wt. Avg. %R valueP-valueR valueP-value Bozeman Intrastate < <.0001 Bozeman Intrastate < Kalispell Intrastate < Bozeman Soft White ns Kalispell Soft White Bozeman Advanced < <.0001 Bozeman Sawfly < <.0001 Bozeman Preliminary A < <.0001 Bozeman Preliminary B < ns Bozeman S. Reg. Perf ns ns Bozeman N. Reg. Perf ns ns Bozeman W. Reg. Hard ns ns Bozeman W. Reg. Soft ns Bzn. Statewide Triticale ns Bzn. PPO/Protein Test < <.0001 Grey, 2006

Stripe Rust Corr. w/ YieldCorr. w/ Test Wt. Avg. %R valueP-valueR valueP-value Bozeman Intrastate < <.0001 Bozeman Intrastate < Kalispell Intrastate < Bozeman Soft White ns Kalispell Soft White Bozeman Advanced < <.0001 Bozeman Sawfly < <.0001 Bozeman Preliminary A < <.0001 Bozeman Preliminary B < ns Bozeman S. Reg. Perf ns ns Bozeman N. Reg. Perf ns ns Bozeman W. Reg. Hard ns ns Bozeman W. Reg. Soft ns Bzn. Statewide Triticale ns Bzn. PPO/Protein Test < <.0001 Grey, 2006

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

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

Fungicides increase yield and test weight in stripe rust susceptible varieties under stripe rust pressure (Bozeman, 2006) Yield (bu/a)Test weight Resistance reaction No fungicide Quadris (14 oz/a) % loss No fungicide Quadris (14 oz/a) Nuwest parent VS BigSky parent VS NuWest VS Rampart parent R McNeal S

Fungicides increase yield and test weight in stripe rust susceptible varieties under stripe rust pressure (Bozeman, 2006) Yield (bu/a)Test weight Resistance reaction No fungicide Quadris (14 oz/a) % loss No fungicide Quadris (14 oz/a) Nuwest parent VS NuWest VS BigSky parent S Rampart parent R McNeal S Grey, 2006

Even ¼ rate fungicide at flag leaf stage can improve yield under stripe rust pressure (Bozeman 2006) Fungicide rateYield (bu/a) (100% = 14 oz/a Quilt) Rep 1Rep 2 No fungicide ¼ rate ½ rate ¾ rate full rate

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

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

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

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