Canola Diseases - Washington State University · Disease Situation with Canola • In general, not...
Transcript of Canola Diseases - Washington State University · Disease Situation with Canola • In general, not...
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