Canola Diseases

Timothy Paulitz USDA-ARS

Pullman, WA

Outline

• General overview of disease situation

• Soilborne Diseases Rhizoctonia Sclerotinia

Outline

• Potential new diseases-Blackleg or Phoma stem rot

Disease Situation with Canola

• In general, not many major diseases problems.

• Why? Crop is not extensively grown in area.

• Many pathogens are Brassica-specific, so if other brassicas are not in area, no source of inoculum

Disease Situation with Canola

• Dry summer climate- no summer rainfall, reduces foliar diseases

• Fungi need free water on leaf surface for spores to germinate.

• However, under irrigation, can become a problem.

Disease Situation with Canola

• However, if pathogens are brought in on infected seed or movement of soil, they can become established.

Disease Situation with Canola

• Critical to use certified disease-free seed especially for blackleg.

Rhizoctonia

• Damping-off of seeds (do not emerge)

• Wirestem- killing of young seedlings

• Root rot of tap root

R. solani AG 2-1: Brassica and canola pathogen

Five Rhizoctonia groups

Management

• Crop rotation not beneficial, because of wide host range.

• Evidence that AG 2-1 can survive on wheat or barley, but does not damage them

Management

• Seed treatments do not protect against wirestem or root rot.

• Resistance- best solution for the future

Sclerotinia- White Mold

• Infects from sclerotia in field and by spores that are ejected and land on blossoms

• Needs wet, humid conditions

Sclerotinia Management

• Start with clean seed- not infested with sclerotia

• Fungicide sprays- properly timed at flowering, based on forecasting.

• Restrict irrigation at flowering

Sclerotinia Management

• Crop rotation- need 4 years, because sclerotia survive in soil

• Cereals and grasses not affected

• All broadleafs are hosts- potato alfalfa, peas

Blackleg

• Most important disease in Canadian Prairies and Midwest, but not found in dryland areas of PNW

• ID and WA were considered blackleg-free

• However, blackleg was discovered in summer-fall, 2011 in Boundary CO, ID, Bonner’s Ferry

Blackleg

• Seed-borne • Once it is established, can

spread by splash or airborne spores

• Survives in crop residue

Blackleg - What is it?

– Caused by the fungus Leptosphaeria maculans

Where does it attack & cause symptoms?

Where does it attack & cause symptoms?

What is Blackleg?

Blackleg Management

• Prevention- Start with disease-free certified seed. Don’t bring it in from other farmers. Use fungicide seed treatments

Blackleg Management

• Crop rotation- 3 years between canola or brassica crops.

• Control volunteers and wild mustards

Blackleg Management

• Resistance- higher in Argentine (B. napus) compared to Polish cultivars (B. rapa).

Blackleg Management

• Tillage- bury canola residues

• Foliar protective fungicide sprays.

Disease Management Guidelines

• 2011 Pacific Northwest Plant Disease Management Handbook

http://plant-disease.ippc.orst.edu/ • Compendium of Brassica Diseases,

2007. APS Press • Canola Council of Canada

http://www.canolacouncil.org/chapter10c.aspx

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Questions?

Control

G7082-00

Prosper 400 Helix XTra Maxim 4FS

Chemical seed treatment test Aug. 2006 Soils inoculated with Rhizoctonia solani AG2-1 (100 ppg)

Non-Inoculated Inoculated with R. solani AG 2-1

Screening Brassica lines for Rhizoctonia resistance

0 ppg 5 ppg 10 ppg 50 ppg 100 ppg

Inoculum density test with Rhizoctonia solani AG2-1 on canola

• Rhizoctonia solani AG-8: Wide host range, bare-patch

• R. oryzae: Pathogenic on cereals and broadleaf crops

• R. solani AG-2-1: Brassica and canola pathogen

• R. solani AG-10: Pathogenic on broad-leaf crops, not much on cereals Binucleate Rhizoctonia (Ceratobasidium AG-I): Pathogenic on broadleaf, not much on cereals

Five Rhizoctonia groups

Control Binucleate Quincy 3

Control Binucleate Quincy 3

Control Binucleate Rhizoctonia Ceratobasidium AG I