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Diagnosing and Managing Diseases of Wheat

Tim Murray, Extension Plant PathologistRachel Bomberger, Diagnostician

WSCIA Annual MeetingNovember 18, 2019

Fungal Diseases of Wheat in the PNWCommon name Pathogen

Stripe rust Puccinia striiformis

EyespotOculimacula yallundae, O. acuformis

Cephalosporium stripe Cephalosporium gramineum

Rhizoctonia root rot Rhizoctonia solani, R. oryzae

Fusarium foot rotFusarium culmorum, F. pseudograminearum

Pythium seed/root rot Pythium spp.

Snow moldsTyphula ishikariensis, Microdochium nivale

Leaf rust Puccinia recondita

Stem rust Puccinia graminis

Virus & Bacterial Diseases of Wheat in the PNW

Common name Pathogen

Barley yellow dwarfBarley yellow dwarf virus, Cereal yellow dwarf virus

Black chaff Xanthomonas translucens

Soilborne wheat mosaic Soilborne wheat mosaic virus

Wheat streak mosaic Wheat streak mosaic virus

PNW Agronomic Production Zones

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Distribution of Diseases by Rainfall

DiseaseRainfall zone

8‐12” 12‐18” >18” Irrig.

Stripe rust

Eyespot

Cephalosporium stripe

Rhizoctonia root rot

Fusarium crown rot

Pythium root rot

Snow molds

Barley yellow dwarf

Soilborne wheat mosaic

Management Considerations

DiseaseCultural practices

Variety selection

Chemicalcontrol

Stripe rust + + +

Eyespot + + +

Ceph. stripe + + ‐

Rhizoctonia root rot + ‐ ‐

Fusarium crown rot + ‐ ‐

Pythium root rot + ‐ +

Snow molds + + ‐

Barley yellow dwarf + ‐ +

Soilborne wheat mosaic ‐ + ‐

Cultural Management Practices

DiseaseSeeding date

Residue mgt

Green bridge

FertilityCrop 

rotationSoil pH

Stripe rust + ‐ + + ‐ ‐

Eyespot + +/‐ ‐ ‐ ‐ ‐

Ceph. stripe + +/‐ ‐ ‐ + +

Rhizoctonia +/‐ + + ‐ ‐ ‐

Fusarium + ‐ ‐ + ‐ ‐

Pythium + + + ‐ ‐ ‐

Snow molds + ‐ ‐ ‐ ‐ ‐

BYD + ‐ + + ‐ ‐

SBWM + ‐ ‐ ‐ ‐ ‐

Stripe Rust

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Stripe Rust

Courtesy X. Chen

Factors Affecting Stripe Rust

Favorable temps/moisture for infection‐ temps of 50‐64°F w/6 hrs of dew‐ cool temps best for disease development, but less important than infection

Fall infection‐ susceptible plants in fallWinter survival‐ temperatures during Dec‐Feb

Stripe Rust Outlook – December 2019

What we know:• Rust intensity during summer 2019 was lowest since 2014

• Early planting/emergence + Fall weather = favorable for rust establishment  infected plants found in some early seeded fields 

Going forward:• Winter weather, especially snow cover and temperatures will be key

Stripe Rust Control Options

CulturalGreen bridge managementAvoid early plantingAvoid excessive irrigation (furrow better than sprinkler)

Plant disease resistant varieties preferably those with HTAP resistance

Monitor rust forecast, scout fields, spray fungicides when necessary Scout fields for rust, spray susceptible varieties (>4) or when 1‐5% of plants have active rust

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Stripe Rust Resistance ‐Winter Varieties 

Rating VarietiesR (1,2) AP700 CL, ARS Castella, Bobtail, Bruehl, Cara, Chukar, Farnum, LCS 

Artdeco, LCS Biancor, LCS Drive, LCS Evina, LCS Ghost, LCS Hulk, LCS Shark, LCS Shine, LCS Sonic, LCS Yeti, LCS Zoom, Legion, Madsen, Norwest 553, Norwest Duet, Norwest Tandem, Otto, Pritchett, Resilience CL+, Sprinter, SY Assure, SY Banks, SY Clearstone CL2, SY Command, SY Dayton, SY Raptor, SY Touchstone, WB523, WB1070CL,  WB1376CLP, WB1529, WB1532, WB1604, WB4623CLP, Whetstone

MR (3,4) ARS Crescent, ARS Selbu, Coda, Jasper, LCS Rocket, Masami, Mela CL+, ORCF 102, Rosalyn, Sequoia, SY Ovation, UI‐WSU Huffman, WB456, WB528, WB4303, WB Arrowhead

M (5) AP503 CL2, AP Badger, Curiosity CL+, Eltan, LCS Jet, Mary, SY 107

MS (6,7) AP Legacy, Keldin, LCS Aymeric, LCS Fusion AX, UI Castle CL+, UI Magic CL+, UI Palouse CL+, WB4059CLP, WB4311, Xerpha

S (8,9) ORCL 103, WB Rimrock

Soft white, Hard red, Club, Hard White

Stripe Rust Resistance ‐ Spring Varieties

Rating VarietiesR (1,2) Expresso, JD, Seahawk, SY Basalt, SY Teton, WB9229, WB9518, 

WB9668

MR (3,4) Alum, Cabernet, Chet, Dayn, Diva, LCS Iron, Louise, Melba, Ryan, SY Coho, SY Gunsight, SY Steelhead, UI Platinum, UI Stone, WB4394, WB6121, WB Hartline, SY Saltese

M (5) Bullseye, Glee, SY Selway

MS (6,7) Hollis, LCS Luna, Tekoa

S (8,9) Babe, Buck Pronto, Kelse, SY605 CL, WB1035 CL+, WB6341, Whit

Soft white, Hard red, Club, Hard White

Infection type

Severity (%)

0 1 2 3 4 5 6 7 8 9

0 1 5 10 20 30 40 50 60 70 80 90 100

What Does 5% Rust Look Like?

Courtesy X. Chen

Rust Fungicides ‐ 2019

Class Active ingredient Product Rate/A, (fl. oz) Stripe rust Leaf rust Stem rustHarvest 

Restriction

Strobi

lurin Picoxystrobin Aproach SC 6.0 – 12.0 E3 VG VG Feekes 10.5 

Pyraclostrobin Headline SC 6.0 ‐ 9.0 E3 E G Feekes 10.5

Triazole

Metconazole Caramba 0.75 SL 10.0 ‐ 17.0 E E E 30 daysTebuconazole Folicur 3.6 F5 4.0 E E E 30 daysProthioconazole Proline 480 SC 5.0 ‐ 5.7 VG VG VG 30 daysProthioconazoleTebuconazole Prosaro 421 SC 6.5 ‐ 8.2 E E E 30 days

Propiconazole Tilt 3.6 EC5 4.0 VG VG VG Feekes 10.5.4

Mixed

 modes of action6

TebuconazoleTrifloxystrobin

Absolute Maxx SC 5.0 VG E VG 35 days

CyproconazolePicoxystrobin

Aproach Prima SC 3.4 ‐ 6.8 E VG ‐‐ 45 days

ProthioconazoleTrifloxystrobin

Delaro 325 SC 8.0 VG VG VGFeekes 10.535 days

PydiflumetofenPropiconazole

Miravis Ace SE 13.7 VG VG VG Feekes 10.5.4

FluxapyroxadPyraclostrobinPropiconazole

Nexicor EC 7.0 ‐ 13.0 E E VG Feekes 10.5

FluoxastrobinFlutriafol

Preemptor SC 4.0 ‐ 6.0 E VG ‐‐Feekes 10.5 and

40 daysFluxapyroxadPyraclostrobin

Priaxor 4.0 ‐ 8.0 VG VG G Feekes 10.5

PropiconazoleAzoxystrobin

Quilt Xcel 2.2 SE5 10.5 ‐ 14.0 E E VG Feekes 10.5.4

ProthioconazoleTrifloxystrobin

Stratego YLD 4.0 VG VG VGFeekes 10.535 days

BenzovindiflupyrPropiconazoleAzoxystrobin

Trivapro SE 9.4 ‐ 13.7 E E VGFeekes 10.5.4

14 days

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Eyespot Lodging

Eyespot 

Stem Lesion

Eyespot

• Reduced growth

• Lodging

• Plants not dead!

• Scout after jointing

• Whiteheads– Sooty head molds

• Infects fall through spring– Lots of water increases severity– Seen more severe, early last year!

• Diamond/football shape with brown and diffuse golden-yellow

Sharp Eyespot

• Less frequent– Increasing in Willamette Valley, OR

• Rhizoctonia– Not the same as root rot

• Dark brown diamond/football shape– Sharp border, no yellow

• Snow mold weather=sharp eyespot weather– May also see wet, matted

appearance of snow mold

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Wheat Doctor / Doctor Trigo by CIMMYT, Int.

Eyespot Pathogens 

O. yallundaeO. acuformis

Old name = CercosporellaNow = Oculimacula

Sporulation on strawOct.

Eyespot Disease Cycle

Rain‐splash spreads spores

Infection and colonization of leaf sheaths 

Dec.

Colonization of true stems

May

Death ofinfectedstems June

Survival in straw Aug.

Factors Affecting Eyespot

Autumn temperatures

Rainfall

Snow cover

November 2019 outlook:

‐ Favorable planting/emergence conditions + low October temps + dry fall conditions = low‐average risk

‐ Scout fields of susceptible varieties prior to jointing to determine severity

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Control of Eyespot

Cultural practices

seeding date

Resistant varieties

Foliar fungicides

Eyespot Resistant Winter Varieties

• ARS Selbu• Brundage 96• Cara• Chukar• Coda• Dyna‐Gro Impact

• Jasper• LCS‐Drive• LCS‐Jet

• Rosalyn• SY Banks• SY Dayton• SY Raptor• SY Touchstone• Tubbs 06 • WB 1529• WB 1532• WB 1604• WB 1783

Soft white, Hard red, Club

• Madsen• Masami• Norwest 553• Norwest Duet• Norwest Tandem• ORCF‐102• Otto• Puma• Purl• Resilience CL+

When to Spray?

“the 10% rule”

• Collect enough plants at spray time to give 50 stems

• Wash and separate into healthy and diseased

• Consider spraying when 5/50 are diseased

Sporulation on strawOct.

Eyespot Disease Cycle

Rain‐splash spreads spores

Infection and colonization of leaf sheaths 

Dec.

Colonization of true stems

May

Death ofinfectedstems June

Survival in straw Aug.

Spray Time 

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Fungicides Registered for Eyespot 

Tilt + Topsin‐M (4 oz + 10 oz)(propiconazole + thiophanate‐methyl)

Alto + Topsin‐M (3.0‐5.5 oz + 10 oz)(cyproconazole + thiophanate‐methyl) 

Nexicor (9‐13 oz) (fluxapyroxad + pyraclostrobin + propiconazole)

Priaxor (3‐4 oz) 

(fluxapyroxad + pyraclostrobin)

Quilt + Topsin‐M (14 oz + 10 oz)(propiconazole + azoxystrobin + thiophanate‐methyl)

Trivapro (13.7 oz) (propiconazole + azoxystrobin + benzovindiflupyr)

Cephalosporium stripe

Cephalosporium Stripe

Early Root rots versus Cephalosporium Stripe

Rhizoctonia/Pythium

• Infection both fall and spring

• Acidic soil (maybe?)

• Cooler, wetter encourages

• Symptoms in roots

• Rhizoctonia slowed maturity (=no whitehead)

• Pythium whiteheads

Cephalosporium Stripe

• Infection occurs in Fall

• Low, wet, acidic soil

• Cool weather

• Symptom Scouting– Later winter/early spring

=ambiguous leaf symptoms

– Jointing=classic yellow stripe extending through nodes

• Brown discoloration in node

• Whiteheads

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Jeff Johnston, Montana State University, Bugwood.org

What looks a bit like this?

What could we look for to distinguish?

No photo credit information available Downloaded from https://guide utcrops com/wheat/wheat disease identification/diseases affecting leaves/cephalosporium stripe/

Factors Affecting Cephalosporium Stripe 

Autumn temperatures

Rainfall

Soil freezing

Soil pH

Controlling Cephalosporium Stripe

Cultural Practices

• Seeding date

• Crop Rotation

• Soil pH modification

Resistant/tolerant varieties

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Influence of Soil pH on Cephalosporium Stripe

pH 4.5 pH 7.5

Control ControlInoculated Inoculated

Confirmed pH response in Washington

Love & Bruehl, 1987

Effect of Soil pH on Cephalosporium Stripe and Take‐all

27.7

32.5

15

19.817.5

0.7

10.2

6.4

51.1

6.8

11.8

56.1

0

10

20

30

40

50

60

CONTROL SULFUR LIME

% D

isea

se

Treatment

Ceph str '82 Ceph str '83

Take-all '82 Take-all '83

Bockus & Classen, 1985

pH 4.8

pH 4.7

pH 6.6

pH 4.5

pH 4.6

pH 6.5

Tolerance to Cephalosporium

• Bobtail• Bruehl• Coda• Curiosity CL+• Eltan• Farnum• Jasper• Keldin• LCS‐Artdeco• LCS Drive

• LCS Jet• Masami• Mela CL+• Norwest Duet• Norwest Tandem

• ORCF 103• Pritchett• Skiles• SY Dayton

Soft white, Hard red, Club

• SY Touchstone

• UI Palouse CL+

• UI Magic CL+• WB 528• WB 1529• WB 1532• Whetstone• Xerpha

Snow Mold Diseases

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Snow Mold Diseases

Speckled snow mold(Typhula ishikariensis)

Pink snow mold(Microdchium nivale)

Gray snow mold(Typhula incarnata)

Pythium snow mold(Pythium spp.)

Snow Mold Diseases 

2 weeks after snow melt

2 months after snow melt

Snow Molds

Pink Snow Mold

• Microdochium

• All grasses affected

• Requires wet, cold conditions– Frost, rain, fog, ect.

• Wet, matted appearance

• Cottony mycelium

• Orange-red-pink coloring

• Patches of damaged plants

Typhula Snow Molds

• Speckled/Grey snow molds

• All grasses affected

• Require snow cover for extended time

• Wet, matted appearance

• Cottony mycelium

• Color is off yellow

• Patches of damaged plants

• Sclerotia embedded in tissue

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Photo by Bob Powelson (care of M. Putnam).

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Resistance to Snow Molds

• Boundary• Bruehl• Curiosity CL+• Eltan• Farnum• Keldin• Mela CL+

• ORCF 103• Otto• Sequoia• UICF Brundage• WB‐Arrowhead• Xerpha

Soft white, Hard red, Club

Rhizoctonia root rot

Photos courtesy of Dr. Tim Paulitz

Pythium and Rhizoctonia

Pythium

• Cool, wet– Fall through Spring

• Seedling stage

• Winter green-up

• Clay soils– Take longer to warm up/dry

• Low spots

• Poor growth, thin

• Yellowing (N deficient-like)

Rhizoctonia

• Mild, wet– Fall through Spring

• Seedling stage

• Winter green-up

• Clay soils– Take longer to warm up/dry

• Often circular, patchy, uneven height

• Green Bridge Phenomena

• Poor growth, missing

• Yellowing (N deficient & drought-like)

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Credit: Tim Paulitz

51 lb/bu

U.S. #5

60 lb/bu

U.S. #1Slide courtesy of Dr. Richard Smiley

Fusarium crown rot

Fusarium Dryland Foot Rot and Take-all

Fusarium Dryland Foot Rot

• Warm weather, drought stressed

• Wet, humid may lead to Fusarium Head Blight

• White heads– Sooty molds

• Chocolate brown discoloration under nodes

• Induced drought stress

Take-all

• Less frequent

• Prefers alkaline soil

• More frequent in irrigated land

• Stunted

• Few, brittle roots

• White heads– Sooty molds

• Black, shiny discoloration to stem/leaf sheath

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Credit:Tim Paulitz

Fusarium Diseases

Fusarium Dryland Foot Rot

• Drought stressed plants– Summer– High/exposed spots– N Fertility – Variety (high protein)

• Four species– Three of which can cause FHB

Fusarium Head Blight

• Only occurs during head emergence-heading if:– Irrigation, high humidity– Corn in rotation/nearby

• Scout for premature head discoloration or odd tan florets while heads should be green!

• 17 species possible—3 common

Aluminum vs Root Rots

High Aluminum

• Bright white roots

• Same volume of roots

• Twisted, clubbed, distorted

• Low pH

Root Rot

• Discolored

• Fewer roots

• Damaged roots

• No root hairs

• Cysts-if cereal cyst nematode is the cause

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© CSIRO Plant Industry 2014

Leaf Spotters

Stagnospora Blotch

• Early Spring

• Lower leaves

• Irregular ovals or flecks with yellow halo

• Tiny fruiting bodies

• Can discolor spikelets too– Looks like bacterial infection too

Septoria Blotch

• Wet, cool weather

• Lower leaves

• Streaks brown and yellow

• Fruiting bodies in necrotic tissue

• Two consecutive rain days increases likelihood

Tan Spot

• Oval-ish spots

• Brown surrounded by yellows

• No fruiting body on leaves (old straw in spring has fruiting bodies

• Are you SURE it isn’t physiological leaf spot?

Physiological Leaf Spot

• Varietal responses

• Often low chloride/zinc

• Leaching conditions

• MOST COMMON!

Maccheek via wikipedia

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Soilborne Wheat Mosaic ‐ SBWM

SBWM Variety Trial, Umatilla, OR 2011

Irrigated circle on sandy soil with severe SBWM symptoms in 2010

Viruses

Wheat Soilborne Mosaic

• Soil microorganism

• Patchy in field – Wet, low areas

• MUST catch leaf symptoms in late winter/early spring– After breaking dormancy

Wheat Streak Mosaic

• Tiny Eriophyid Mite

• Wide cereal host range

• Late-harvested crops and irrigated fields most likely

• First observed on field edges

• Curling of lower leaves– Mites often observed

Barley Yellow Dwarf

• Aphid vector

• Yellow flag leaf– Or red, or purple, or green, or

brown, or orange

• Short internodes (‘Dwarf’)

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SBWMV

Photo by Phil Hamm credit to Texas A&M Soil and Crop Sciences

SBWMVEmmanuel Byamukama, South Dakota State University, Bugwood.org

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Barley Yellow Dwarf

Barley Yellow Dwarf

Courtesy S. Reinertsen

BYDV Vectors

SGV

Metopolophium dirhodumRose-grass Claude Pilon

Sitobion avenae English grainClaude Pilon

Rhopalosiphum padiBird-cherry Oat

Tom Murray

Schizaphis graminumGreenbug

Viarural.com

Rhopalosiphum maidisCorn leaf

Insects.tamu.edu

SBWM

Disease of fall‐sown wheat

Transmitted by soilborne fungus‐like organism

acts like other soilborne diseases in terms of distribution within fields and spread

Infection occurs in the fall and symptoms appear in early spring

‐ symptoms fade and plants appear to recover as temperature increases in spring

Damage remains and yield is reduced

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SBWM – Management

Disease resistance – only practical option

WB1066CL

0 Rating146 bu/ac

Coda 9 Rating50 bu/ac

SBWMV Resistant Varieties

• ARS Pritchett• Genesis• Ladd• LCS Shark• ORCF‐103• ORCF‐101

Soft white, Hard red, Club

• Puma• SY Dayton• SY Ovation• WB4303• WB Junction• Whetstone

Management Considerations

DiseaseCultural practices

Variety selection

Chemicalcontrol

Stripe rust + + +

Eyespot + + +

Ceph. stripe + + ‐

Rhizoctonia root rot + ‐ ‐

Fusarium crown rot + ‐ ‐

Pythium root rot + ‐ +

Snow molds + + ‐

Barley yellow dwarf + ‐ +

Soilborne wheat mosaic ‐ + ‐

Cultural Management Practices

DiseaseSeeding date

Residue mgt

Green bridge

FertilityCrop 

rotationSoil pH

Stripe rust + ‐ + + ‐ ‐

Eyespot + +/‐ ‐ ‐ ‐ ‐

Ceph. stripe + +/‐ ‐ ‐ + +

Rhizoctonia +/‐ + + ‐ ‐ ‐

Fusarium + ‐ ‐ + ‐ ‐

Pythium + + + ‐ ‐ ‐

Snow molds + ‐ ‐ ‐ ‐ ‐

BYD + ‐ + + ‐ ‐

SBWM + ‐ ‐ ‐ ‐ ‐

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Wheat and Small Grains websitehttp://smallgrains.wsu.edu/Twitter @WSUWheatDoc

Stripe rust alerts: updates by Dr. Chen begin in January

• http://striperustalert.wsu.edu/

Variety Ratings: Stripe rust, eyespot, Cephalosporium stripe• WSCIA seed guides• Variety Selection Tool

Disease Information Resources

Diagnosis of Problems

Questions?