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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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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?