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

Dr. Mary BurrowsMontana State University Bozeman, MT

Why was stripe rust so bad this year?1. Widespread fall infection2. Extended fall3. Deep, lengthy snow cover4. Favorable spring temperatures5. Flooding created wet, humid conditions throughout

the year6. Even after day temps became hot, night temps were

favorable for infection (50-70F)7. A widely planted, susceptible variety (Genou)8. New strains9. 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

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

Degree day map, 24 May, 2011Reports from Havre, Fort Benton, Great Falls

Mary: “Genou is what??? Send a sample”

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

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

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

The rusts of wheat

Jim Berg, MSU

Stripe Stem Leaf

Yellow Black Red

Rust diseases are not mutually exclusive

Leaf rust, stem rust: ‘Puccinia pathway’

Stripe rust: gen’l WA or Canada

Normally, this is wheat

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

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

Yellowstone

PromontoryJohnston & Grey, 2006

Susceptible varietyResistant variety

CDC Falcon Yellowstone

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

Yellowstone

PromontoryJohnston & Grey, 2006

Susceptible varietyResistant variety

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 Wheat http://plantsciences.montana.edu/Crops/2011data/2011WinterWheatVarieties.pdf

Tables 3, 4, and 14

Tolerant Moderate SusceptibleJagalene Above BigSky

Jerry Hatcher CDC Buteo

Judee NuWest CDC Falcon

Ledger Rampart Genou

NuFrontier Rocky Morgan

Yellowstone Vanguard Neeley

Wahoo NuWest

NuSky

Pryor

Current classifications: Spring wheat http://plantsciences.montana.edu/Crops/2011data/2011WinterWheatVarieties.pdf

Pages 23 and 24

Tolerant Moderate SusceptibleBrennan Conan AP604CL

Bynum Corbin Hank

Choteau Hyalite

Freyr Jedd

Jenna Knudsen

Kelby McNeal

Reeder Mott

Vida Norris

Volt ONeal

Note: this needs to be updated with 2011 data

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

Yield of control Yield loss (%) Yield Inc. (%)Cultivar (bu/A) by stripe rust by fungicideAP700CL 116.76 -1.43 -1.41Madsen 110.12 1.06 1.07Chuckar 106.62 7.14 7.68Rod 104.87 -1.63 -1.61Stephens 102.07 12.34 14.08Brundage 96 98.37 11.36 12.82Westbred 528 97.44 9.95 11.05Bruehl 95.27 6.65 7.12Buchanan 93.32 -4.77 -4.56ORCF-102 90.04 12.22 13.92Masami 86.10 14.44 16.88Eltan 85.99 10.48 11.71ORCF-103 83.07 14.67 17.19Cashup 78.78 10.59 11.84Tubbs 06 78.75 23.03 29.93Eddy 71.37 22.87 29.65Xerpha 70.49 26.15 35.40Bauermeister 67.28 20.61 25.96Farnum 66.43 2.22 2.27Lambert 64.43 33.34 50.01Paladin 63.72 20.38 25.60Finley 61.70 5.04 5.31Declo 42.15 44.00 78.58PS 279 29.88 54.17 118.19Mean 81.88 14.79 21.61Mean (Excl. PS 279) 84.14 13.07 17.41

Resistant check

Susceptible check

Fungicides

Ron Muzzana, 2011

Strobilurins TriazolesMode of action FRAC 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

Residual 14-21 days of protection

14-21 days of protection

Resistance development

High (specific MOA) Medium

Mobility in plant Translaminar and systemic

High

Protection Protective only (kill germinating spores)

Protective and curative

Note: these are generalizations about fungicide classes

50556065707580859095

100

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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 bb

c c c c

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)

Treatment Rate Active ingredient(s) Company Hill Co.(var. Genou)

Toole Co.(var. Genou)

Liberty Co. (var.

Genou)

Control 11.25 4.625 2.5

Headline 3 oz/A Pyraclostrobin BASF 3.75 0.375 0

Headline 6 oz/A Pyraclostrobin BASF 0.125 0 0

Quilt 7 oz/A Azoxystrobin + Propiconazole Syngenta 1.25 0 0

Quilt 14 oz/AAzoxystrobin + Propiconazole Syngenta 0 0 0

Stratego 4 oz/A Trifloxystrobin + Propiconazole Bayer 1.375 0.125 0

Stratego 8 oz/A Trifloxystrobin + Propiconazole Bayer 0 0 0

Quadris 4 oz/A Azoxystrobin Syngenta 1.25 0 0

Tilt 2 oz/A Propiconazole Syngenta 0 0 0

Sprayed too early for max SR

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

TreatmentYield (bu/A)

Disease (% flag leaf area

29 June)

Untreated control 25.8 8.2 a

Headline SC 3 oz/A 29.8 4.2 b

Headline SC 6 oz/A 29.5 2.9 bcd

Quilt  Xcel 14 oz/A 34.2 1.6 ef

Quilt  Xcel 7 oz/A 32.4 2.3 def

Stratego 8 oz/A 37.6 2.0 def

Stratego 4 oz/A 31.3 3.4 bc

Tilt 4 oz/A 28.7 2.4 cdef

Tilt 2 oz/A 23.8 1.8 ef

Quadris flowable 12 oz/A 31.6 1.5 f

Quadris flowable 6 oz/A 25.5 2.7 bcde

P-value >0.10 <0.001

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

Product Rate Timing

Disease12 Aug (% flag)

Incidence12 Aug

(%)Yield (bu/A)

Control 23 70 81 bc

Stratego YLD + Wolverine

1.5 oz/A + 1.7 pt/A

Tillering 32 95 84 abc

Stratego YLD 3 oz/A Tillering 17 83 80 c

Stratego YLD 1 oz/A Flag 2 40 86 ab

Absolute 500 SC

3 oz/A Flag 0 0 87 a

Prosaro 421 SC

3 oz/A Flag 0 6 81 bc

Prosaro 421 SC

4 oz/A Flag 0 5 86 ab

Prosaro 421 SC

10.5 oz/A Flowering 0 5 85 abc

P = 0.11

Glume infection of stripe rust

‘Rescue’ spraying?

Remember your PHI!

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

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 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.

A number of new strains were characterized after a severe epidemic in 2000

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.

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How do new

strains originate?

Aecia on barberry

Uredinia on Kentucky bluegrass

Pycnidia on barberry

Aecia on barberry Uredinia on wheat

Jin, Szabo and Carson, Plant Dis., 2010

What qualifies as excitement for a plant pathologist:

2010 Stripe rust strains (PSTv-#)

16,1414 38

14, 44

22,39

46

2011 Stripe rust strains (PSTv-#)Data updated 9 Dec, 2011

11

11

11,14 14

14

14

14,3714,37

37

17

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

Virulence on differential linesYear Strain 1-10 11-20 21-50 Other2010 PSTv-14 1, 2, 6, 7, 8, 9 17 27, 43, 44 Tr1, Exp2, Tye

PSTv-16 1, 2, 6, 7, 8, 9 17 26, 27, 43, 44 Exp2, Tye

PSTv-22 2

PSTv-38 2, 6, 7, 8, 9 26, 27, 44 Tr1, Exp2

PSTv-39 2, 6, 7, 8, 9 26 Tr1, Exp2

PSTv-45 2, 6, 7, 8, 9 26, 27, 43, 44 Tr1, Exp2

PSTv-46 2, 6, 7, 8, 9 17 26, 27, 43, 44 Tr1, Exp2

2011 PSTv-11 1, 2, 6, 7, 8, 9 17 27, 43, 44 Exp2, Tye

PSTv-14 1, 2, 6, 7, 8, 9 17 27, 43, 44 Tr1, Exp2, Tye

PSTv-17 1, 2, 6, 7, 8, 9 17 27, 43, 44 Sp, Exp2, Tye

PSTv-37 2, 6, 7, 8, 9 17 27, 43, 44 Tr1, Exp2

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

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

Yellowstone

PromontoryJohnston & Grey, 2006

Susceptible varietyResistant variety

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

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

AcknowledgementsDai Ito, Matt Moffet, Zach Miller,Linnea SkoglundMSU County Extension Agents

USPEST.ORG

Which seed treatment to use?• Very little data, and results showing yield benefit may

not be solely due to stripe rust control• Whether any products will prevent overwintering is

unknown• Within-field overwinter inoculum may be lower, but

this is still an airborne disease• Plant disease management reports:

www.planthealthmanagement.org – search for Xianming Chen and stripe rust (PDMR 1: ST005; 1: ST006; 1: ST007)

Contro

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Proline

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Yield, stem rust fungicide trial2009, Bozeman

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Yield, stem rust fungicide trial2011, Bozeman

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Strateg

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Strateg

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Prosaro

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20

30

40

50

60

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Yiel

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Compare sprayed and unsprayed plots

Control (no fungicide), 14 daa

Strobilurin fungicides, 14 daa

Headline

Gem 500 SC

Strobiliurin + Trizole, 14 daaQuilt

Quilt Xcel

Strobiliurin + Trizole, 14 daa

Prosaro

Twinline

Trizole fungicides, 14 daa

Alto

Proline

Caramba