Diseases
Disease Control
Light Leaf Spot (LLS) and Phoma are the main targets for disease control in winter oilseed rape but soil-borne diseases, schlerotinia stem rot, clubroot and verticillium wilt can appear if rotation are short.
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Main Diseases of Oilseed Rape |
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Disease |
Phoma |
Light leaf Spot |
Sclerotinia |
Alternaria |
|
Conditions influencing infection |
Warm weather speeds up infection |
Wet weather (rain splashed) |
Above average temps in April & showery conditions at flowering |
Lodged crops & wet weather |
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Importance in Ireland |
Main autumn target disease |
Main target disease |
Limited |
Important in wet Summer |
|
Infection timing |
Early Autumn |
Early Autumn |
Petal Fall |
Pod development/fill |
|
Rotation (between OSR crops) |
No definite interval but spread from trash |
No definite interval but spread from trash |
A good rotation will help minimise outbreaks. |
No definite interval. Spread from trash and brassica crops. |
|
Source of infection |
Trash from previous crops or infected seed. Airbourne ascospores |
Trash and seed borne Airbourne ascospores in the autumn |
Trash + alternative hosts incl. beet, potatoes & pulses |
Trash & seed borne |
|
Threshold |
10% of plants affected |
None treat as soon as LLS is detected |
Assess risk based on previous cropping history. |
None. Spray if lesions present on pods at the end of flowering |
|
Treatment |
Early Oct & Mid March/April once threshold is observed |
Mid Oct. - early Dec infection may not be visible so spray is preventative. Also Feb- March if threshold is reached. |
Early petal fall - Petals falling onto stems incubate the fungus |
Mid - late flowering |
|
Varietal Resistance |
Yes |
Yes |
No |
No |
|
Yield Losses |
Up to 25% |
Up to 50% |
Up to 50% |
Up to 50 % (Pod shatter) |
For details on fungicide rates and timings contact your local Teagasc advisor