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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.  

Main Diseases of Oilseed Rape


(Stem Canker)

Light leaf Spot



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

Importance in Ireland

Main autumn target disease

Main target disease


 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


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


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





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