What Lurks in Your Canola Field: Disease Surveys of 2009 · What Lurks in Your Canola Field:...

What Lurks in Your Canola Field:Disease Surveys of 2009

Debra McLaren & Anastasia KubinecAAFC-Brandon and MAFRI-Carman

D. McLaren, A. Kubinec, R. Kutcher, S. Strelkov, F. Dokken, P. Northover, S-F. Hwang, R. Howard

and K. Turkington

Studies / Collaborators

Survey of Canola Diseases in ManitobaSurveillance and dispersal of Plasmodiophora

brassicae in western Canada

Manitoba Team for Canola Survey

• Manitoba Canola Growers Association• AAFC

– Deb McLaren, Tom Henderson, Danny Hausermann and Teri Kerley

• MAFRI– Anastasia Kubinec, Brian Jack, Stephanie Jersak,

Hilmar Johnson, Lionel Kaskiw, Ingrid Kristjanson and Kristen Phillips

• Canola Council of Canada– Derwyn Hammond

• 140 canola fields in Manitoba

• 60 of these fields = soil samples for clubroot

Canola Fields for Survey in Manitoba

Bruce Barker Bruce Barker

Red = disease survey + soil sample

Green = disease survey only

In The Field 20 paces

100 paces

100 paces

Sanitation Practices for Canola Survey

• Wear disposable booties and disposable rubber gloves

• Sterilize soil sampling equipment in bleach after leaving field but before entering vehicle

• Eliminate transport of infected soil outside of the sealed soil sample.

• Do not drive into the field

Soil Collection for Clubroot Assessment

• Collect 1 L soil from all 5 points of W combined

• If entrance to field is obvious, collect soil from 5 points in area limited to the vicinity of this approach.

• To collect soil, clear away crop residue and scoop approx. 1 cup soil from top 5-10 cm

• Place in paper bags to air-dry.

Canola Diseases

Sclerotinia Stem RotBlackleg

Alternaria Black SpotAster YellowsFusarium Wilt

Foot RotClubroot

Sclerotinia Stem Rot: Sclerotinia sclerotiorum

Canola Council of Canada

Frayed Stems and Presence of Sclerotia

Premature Ripening & Crop Lodging



Rating for Sclerotinia Stem Rot

• Main stem lesions that affected the entire plant were recorded separately from any lesion in the upper branches or pods

Sclerotinia Stem Rot in Manitoba (2009)

Crop RegionNo. of Crops Prevalence (%) Incidence

Central 49 96 19

East./Interlake 20 100 37

Northwest 23 96 20

Southwest 48 81 7

Province 140 91 18

Canola Council

Sclerotinia in Canola: Previous Years

Year No. of Crops Prevalence (%) Incidence

2008 54 94 23

2007 40 80 5

2006 33 39 3

2005 81 40 3

2004 68 72 9

Blackleg: Leptosphaeria maculans

Whitish, round to irregular lesions on leaves dotted with pycnidiaLesions on leaves become papery and dryBrown to greyish black lesions, become sunken cankers , girdling the stemBlack lines inside base of stemPremature plant death

Blackleg

Damage due to blackleg basal stem cankers

Blackleg on

canola pod

and upper

stem

Blackleg Rating System

• Main stem lesions that affected the entire plant were recorded separately from any lesion(s) in the upper branches or pods

• Cankers formed early in the season may girdle the stem (virulent strain – L. maculans)

• Weakly virulent strain (L. biglobosa) also causes stem lesions but superficial, non-girdling and occur late in the season so don’t affect yield

Blackleg in Manitoba Canola Fields (2009)CCC

Basal Cankers Upper Stem Lesions

Crop Region

PercentPrevalence Incidence


Central 76 8 76 5

East./Inter. 75 4 60 2

Northwest 22 2 43 7

Southwest 44 2 40 1

Province 56 4 56 4

Blackleg in Canola: Previous YearsCCC

Basal Cankers Upper Stem Lesions

Crop Region



2008 17 3 54 7

2007 52 2 65 7

2006 39 7 61 5

2005 60 4 65 6

2004 32 6 35 5

Alternaria Black Spot



•Brown to black small, round spots onpods and stems•As disease progresses, spots become black to gray with black border •Leaves die and drop off•Pods become dry and sunken and split prematurely

Rating Scale for Alternaria Black Spot

Alternaria black spot on canola

Conn et al. 1990


Crop RegionNo. of Crops Prevalence (%)

Disease Severity

Central 49 47 <1

East./Interlake 20 85 <1

Northwest 23 22 <1

Southwest 48 23 <1

Province 140 40 <1

* Generally a 1% infection of pods or stems translates into a 1% yield loss.

Fusarium Wilt (F. oxysporum f.sp. conglutinans)


• In some plants, yellowing & necrosis affects one side of stem, or individual branches

Distinct colour: grey-green with a red-pink cast

Healthy

Fusarium Wilt


Central 49 2 <1


Northwest 23 0 0

Southwest 48 4 <1

Province 140 4 <1

Fusarium Wilt : Previous Years


2008 54 9 1

2007 40 15 <1

2006 33 18 1

2005 81 21 1

2004 68 0 0

Aster Yellows

Diseases of Field Crops in Canada, CPS

Aster Yellows

•Transmitted by asterleafhoppers

•Malformation of the floral parts•Round to oval blue-greenish,hollow bladder like formations

Aster Yellows


Central 49 14 <1


Northwest 23 13 <1

Southwest 48 15 <1

Province 140 15 <1

Foot RotDiseases of Field Crops in Canada

• Early symptoms of light brown lesions on roots(taproot and/or mainlateral roots) below soilline

• Lesions enlarge, leavinga “stubby root

• Plants ripen prematurely

Foot Rot

• Foot rot was observedin 2% of canola fields

• Disease incidence was<1% in Central, E/I andNW regions.

• No foot rot observed inSW region.

Clubroot : Plasmodiophora brassicae

Sowiak

Turkington

Healthy Root

Strelkov

Young RootGalls

Clubroot

Range of Clubroot Symptom Severity

Healthy

Diseases of Field Crops in Canada

Sowiak

Turkington

Decaying ClubrootGalls

Disintegration and spore release

Why is Clubroot of Concern?

• Serious disease of canola, mustard and other crops in the cabbage family

• Spreads through resting spores in soil• Resting spores are extremely long lived• This can be problematic under tight rotations• Infestations near 20% cause yield loss of

10%• Yield and quality (oil content) of the seed are

reduced

Clubroot – Life Cycle of Pathogen

Clubroot Status (Oct. 2009)

• Clubroot confirmed in 454 fields since 2003

• 224 fields visited & 49 new cases identified in 2009

• 17 municipalities & City of Edmonton– Additional cases suspected

but not confirmed• Presence of P. brassicae

inoculum also confirmed in Saskatchewan (1 field in 2008)

• Presence in Manitoba in one canola field in 2005.

What is being done about Clubroot?

• April 2007 – clubroot added as a declared pest to Alberta’s Agricultural Pest Act.

• June 2009 – clubroot declared a pest in SK under The Pest Control Act.

• Not a legislated pest in Manitoba yet but this is in progress

• Required to take steps to destroy, control and prevent spread of clubroot.

Potential for Clubroot Infestations – Climex Modelling

Turkington, Olfert & Weiss

Clubroot – Management Strategies

• Use long rotations between crops – 4 yrs or more• Practice good sanitation to restrict movement of

contaminated soil• Soil conservation practices to reduce erosion• Scout regularly to ID causes of wilting, stunting,

yellowing and premature ripening• Avoid common untreated seed because ‘earth tag’

on seed from infested fields could introduce resting spores to clean fields.

• Risk of spreading clubroot through contaminated seed is much less than through transporting contaminated soil on field equipment.

Summary

• Clubroot– Alberta: New cases of clubroot continue to be identified– Saskatchewan: One case of clubroot 2008; no symptoms in 2009; soil

sample results pending– Manitoba: No clubroot symptoms in 2009; soil samples

• Sclerotinia:– Similar levels in past few years

• Blackleg:– prevalence of basal cankers increased; that of stem cankers relatively the

same. • Fusarium wilt:

– prevalence reduced over years

• Survey of Manitoba canola fields:– will continue as a collaboration between AAFC, MAFRI, MCGA, and CCC

Acknowledgements: Technical Staff at AAFC-Brandon

Teri KerleyDanny Hausermann

Tom Henderson

What Lurks in Your Canola Field: Disease Surveys of 2009 · What Lurks in Your Canola Field:...

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