1. Stripe rust and foliar fungicide use Dr. Mary Burrows Montana State University Bozeman, MT

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

3. Rust diseases are not mutually exclusive

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

5. Why was stripe rust so bad this year? 1.Widespread fall infection 2.Extended fall 3.Deep, lengthy snow cover 4.Favorable spring temperatures 5.Flooding created wet, humid conditions throughout the year 6.Even after day temps became hot, night temps were favorable for infection (50-70F) 7.A widely planted, susceptible variety (Genou) 8.New strains 9.April: alerts from Xianming Chen that stripe rust was off to an ‘early start’ in WA

6. Fall infection by stripe rust, 2010

7. Fall 2010: Distribution of stripe rust

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

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

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

11. Normally, this is wheat

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

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

16. CDC FalconYellowstone

17. 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

18. Current classifications: Winter Wheat http://plantsciences.montana.edu/Crops/2011data/2011WinterWheatVarieties.pdf Tables 3, 4, and 14 http://plantsciences.montana.edu/Crops/2011data/2011WinterWheatVarieties.pdf TolerantModerateSusceptible JagaleneAboveBigSky JerryHatcherCDC Buteo JudeeNuWestCDC Falcon LedgerRampartGenou NuFrontierRockyMorgan YellowstoneVanguardNeeley WahooNuWest NuSky Pryor

19. Current classifications: Spring wheat http://plantsciences.montana.edu/Crops/2011data/2011WinterWheatVarieties.pdf Pages 23 and 24 http://plantsciences.montana.edu/Crops/2011data/2011WinterWheatVarieties.pdf TolerantModerateSusceptible BrennanConanAP604CL BynumCorbinHank ChoteauHyalite FreyrJedd JennaKnudsen KelbyMcNeal ReederMott VidaNorris VoltONeal Note: this needs to be updated with 2011 data

20. Xiangming Chen, WSU, 2010 Stripe rust would have caused 54% yield loss in WA without fungicide application in 2010 if all varieties were as susceptible as PS279 If all resistant cultivars were grown, 1% yield loss with no fungicide application Resistant check Susceptible check

21. Fungicides Ron Muzzana, 2011

22. StrobilurinsTriazoles Mode of actionFRAC group 11: QoI (quinone outside) inhibitors (respiration); spore germination, penetration, and mycelial growth FRAC group 3 : DMI (demethylation) inhibitors; biosynthesis of sterols in fungal cell membrane; spore penetration and mycelial growth Residual14-21 days of protection Resistance development High (specific MOA)Medium Mobility in plantTranslaminar and systemic High ProtectionProtective only (kill germinating spores) Protective and curative Note: these are generalizations about fungicide classes

23. Strobilurin fungicides, 14 daa Headline Gem 500 SC Stem rust inoculated trial, 2009, Bozeman

24. Trizole fungicides, 14 daa Alto Proline Caramba Stem rust inoculated trial, 2009, Bozeman

25. 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

26. On-farm/on-station fungicide trials: flag applications (sprayed 9-10 June, rated 7-8 July) Disease severity (plot rating, avg % leaf area covered by active stripe rust pustules) TreatmentRateActive ingredient(s)Company Hill Co. (var. Genou ) Toole Co. (var. Genou ) Liberty Co. (var. Genou) Control 11.34.62.5 Headline3 oz/APyraclostrobinBASF 3.80.40 Headline6 oz/APyraclostrobinBASF 0.100 Quilt7 oz/A Azoxystrobin + Propiconazole Syngenta 1.300 Quilt14 oz/A Azoxystrobin + Propiconazole Syngenta 000 Stratego4 oz/A Trifloxystrobin + Propiconazole Bayer 1.40.10 Stratego8 oz/A Trifloxystrobin + Propiconazole Bayer 000 Quadris4 oz/AAzoxystrobinSyngenta 1.300 Tilt2 oz/APropiconazoleSyngenta 000 Sprayed too early for max SR

27. Stripe rust on WW Bozeman, 2011 – Bynum (Resistant to stripe rust) Treatment Yield (bu/A) Disease (% flag leaf area 29 June) Untreated control25.88.2a Headline SC3 oz/A29.84.2b Headline SC6 oz/A29.52.9bcd Quilt Xcel14 oz/A34.21.6ef Quilt Xcel7 oz/A32.42.3def Stratego8 oz/A37.62.0def Stratego4 oz/A31.33.4bc Tilt4 oz/A28.72.4cdef Tilt2 oz/A23.81.8ef Quadris flowable12 oz/A31.61.5f Quadris flowable6 oz/A25.52.7bcde P-value >0.10<0.001 Sprayed 5 June, Feekes 5, 2011

28. Bynum Winter Wheat: Resistant No yield benefit to tillering or flag fungicide application (Priaxor, Headline, Evito, Quilt Xcel, Twinline study, Bozeman, 2011) Photo: M. Moffet

29. Stripe rust on SW Bozeman, 2011 – Vida – MR to stripe rust ProductRateTiming Disease 12 Aug (% flag) Incidence 12 Aug (%) Yield (bu/A) Control237081bc Stratego YLD + Wolverine 1.5 oz/A + 1.7 pt/A Tillering329584abc Stratego YLD3 oz/ATillering178380c Stratego YLD1 oz/AFlag24086ab Absolute 500 SC 3 oz/AFlag0087a Prosaro 421 SC 3 oz/AFlag0681bc Prosaro 421 SC 4 oz/AFlag0586ab Prosaro 421 SC 10.5 oz/AFlowering0585abc P = 0.11

30. Glume infection of stripe rust

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

32. 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)

33. 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

34. New strains are more aggressive Moon 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”

35. New strains infect plants at higher temperatures Milus, E. A., Seyran, E., and McNew, R. 2006. Aggressiveness of Puccinia striiformis 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.

36. 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 Puccinia striiformis f. sp. tritici in the United States in 2000. Plant Dis. 86:39-46.

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

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

39. 2011 Stripe rust strains (PSTv-#) Data updated 9 Dec, 2011 11 11,14 14 14,37 37 17

40. So what do those numbers mean? Virulence on differential lines of wheat Virulence on differential lines YearStrain1-1011-2021-50Other 2010PSTv-14 1, 2, 6, 7, 8, 91727, 43, 44Tr1, Exp2, Tye PSTv-16 1, 2, 6, 7, 8, 91726, 27, 43, 44Exp2, Tye PSTv-22 2 PSTv-38 2, 6, 7, 8, 926, 27, 44Tr1, Exp2 PSTv-39 2, 6, 7, 8, 926Tr1, Exp2 PSTv-45 2, 6, 7, 8, 926, 27, 43, 44Tr1, Exp2 PSTv-46 2, 6, 7, 8, 91726, 27, 43, 44Tr1, Exp2 2011PSTv-11 1, 2, 6, 7, 8, 91727, 43, 44Exp2, Tye PSTv-14 1, 2, 6, 7, 8, 91727, 43, 44Tr1, Exp2, Tye PSTv-17 1, 2, 6, 7, 8, 91727, 43, 44Sp, Exp2, Tye PSTv-37 2, 6, 7, 8, 91727, 43, 44Tr1, Exp2

41. 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

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

43. So, what about this year? Dry fall! But, open, warm….??? Hot spots due to prevented planting; WW seeded very early Plant a resistant variety Use a seed treatment on SW 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

44. How about fungicide in the absence of disease? Yield (Fungicide - Control, bu/A)

45. Early season fungicide applications on dryland wheat (Stratego, 5 oz. rate, tillering, on-farm, non-replicated) YearRegionWheatNo. fields No. fields with a yield difference from the control of at least 2 bu/A IncreaseNeutralDecrease 2007CentralWW13 1 (7%) 102 EasternSW9 2 (22%) 43 2008CentralWW6 1 (17%) 50 EasternSW6 1 (17%) 00

46. All fungicide trials Profit estimated at 2 bu/A above control (no fungicide) Tillering application Flag application Half rate fungicide 6/27 (22%) 7/24 (29%) 13/51 (25%) Full rate fungicide 8/13 (62%) 28/54 (52%) 36/67 (54%) 14/50 (40%) 33/78 (42%) 49/118 (42%) Data from trials in Montana, 2007-2011; WW and SW # trials profitable (2 bu/A + above control) / # trials Yield benefits of fungicide in wheat in the absence of disease pressure

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

49. www.mtagalert.org Agalerts by email or fax Mary Burrows 994-7766 mburrows@montana.edu Fax: 994-7600 Name, fax, phone no.

50. Acknowledgements Dai Ito, Matt Moffet, Zach Miller, Linnea Skoglund MSU County Extension Agents USPEST.ORG