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Stripe rust and foliar fungicide use. Dr. Mary Burrows Montana State University Bozeman, MT. The rusts of wheat. Stripe Stem Leaf. Jim Berg, MSU. Yellow Black Red. Rust diseases are not mutually exclusive.

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Stripe rust and foliar fungicide use

Dr. Mary Burrows

Montana State University Bozeman, MT


The rusts of wheat

Stripe Stem Leaf

Jim Berg, MSU

Yellow Black Red


Rust diseases are not mutually exclusive


Stripe rust: gen’l WA or Canada

Leaf rust, stem rust:

‘Puccinia pathway’


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


Fall infection by stripe rust, 2010


Fall 2010: Distribution of stripe rust


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


Stripe rust spore cloud: 23 June, 2011 near Kremlin (Hill Co.)

Photo courtesy of Ryan McCormick


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


Normally, this is wheat


Great Falls area, 23 June, 2011

WW Variety: Genou


Yellowstone

Promontory

Johnston & Grey, 2006

Stripe Rust: variety resistance is very effective at reducing yield losses

Susceptible variety

Resistant variety


CDC Falcon

Yellowstone


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


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


Current classifications: Spring wheathttp://plantsciences.montana.edu/Crops/2011data/2011WinterWheatVarieties.pdfPages 23 and 24

Note: this needs to be updated with 2011 data


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


Fungicides

Ron Muzzana, 2011


Note: these are generalizations about fungicide classes


Strobilurin fungicides, 14 daa

Headline

Stem rust inoculated trial, 2009, Bozeman

Gem 500 SC


Trizole fungicides, 14 daa

Alto

Caramba

Proline

Stem rust inoculated trial, 2009, Bozeman


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)


On-farm/on-station fungicide trials: flag applications (sprayed 9-10 June, rated 7-8 July)

Sprayed too early for max SR


Stripe rust on WWBozeman, 2011 – Bynum (Resistant to stripe rust)

Sprayed 5 June, Feekes 5, 2011


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

Photo: M. Moffet


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


Glume infection of stripe rust


‘Rescue’ spraying?

Hunger and Jackson. Foliar fungicides and wheat production in Oklahoma. http://lubbock.tamu.edu/wheat/pdfs/osufoliarfunghandout04.pdf

Remember your PHI!


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)


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


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”


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.


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.


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


2010 Stripe rust strains (PSTv-#)

14

38

16,14

14, 44

22,39

46


2011 Stripe rust strains (PSTv-#)

Data updated 9 Dec, 2011

14

11,14

11

17

14

11

37

14

14,37

14,37


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


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


Yellowstone

Promontory

Johnston & Grey, 2006

Stripe Rust: variety resistance is very effective at reducing yield losses

Susceptible variety

Resistant variety


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


How about fungicide in the absence of disease?

Yield (Fungicide - Control, bu/A)


Early season fungicide applications on dryland wheat(Stratego, 5 oz. rate, tillering, on-farm, non-replicated)


Yield benefits of fungicide in wheat in the absence of disease pressure

Data from trials in Montana, 2007-2011; WW and SW

# trials profitable (2 bu/A + above control) / # trials


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


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


www.mtagalert.org

Agalerts by

email or fax

Mary Burrows

994-7766

[email protected]

Fax: 994-7600

Name, fax, phone no.


Acknowledgements

Dai Ito, Matt Moffet, Zach Miller,

Linnea Skoglund

MSU County Extension Agents

USPEST.ORG


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