Canola Diseases Kurtis Schroeder Department of Plant Pathology Washington State University Pullman, WA
Outline General overview of disease situation Soilborne Diseases Rhizoctonia Sclerotinia Potential new disease Blackleg or Phoma stem rot
Disease Situation with Canola In general, not many major disease problems Why? Crop is not extensively grown in area Many pathogens are Brassicaspecific, 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
Rhizoctonia Damping-off of seeds (do not emerge) Wirestem- killing of young seedlings Root rot of tap root
Rhizoctonia groups 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
Post emergence damping off
Wirestem symptom
Five Rhizoctonia groups 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
Control Binucleate Rhizoctonia Ceratobasidium AG I
Management Crop rotation not beneficial, because of wide host range Evidence that AG 2-1 can survive on wheat or barley
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 from apothecia
Sclerotinia White Mold Spores colonize senescent blossoms or other dead plant material prior to infection 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 All broadleafs are hosts- potato alfalfa, peas Cereals and grasses not affected
Blackleg Most important disease in Canadian Prairies and Midwest, but not found in dryland areas of PNW ID and WA were considered blacklegfree 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 Also referred to as Phoma stem canker
Where does it attack & cause symptoms?
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 Pacific Northwest Plant Disease Management Handbook pnwhandbooks.org/plantdisease Compendium of Brassica Diseases, APS Press www.apsnet.org/apsstore/shopapspress Canola Council of Canada www.canolacouncil.org/crop-production