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The Problem

While the recent snow and cold temperatures may have slowed growth, it’s unlikely to translate into significant crop losses. It is now a case of protecting that potential for an effective return.

Whilst Sclerotinia is usually the main disease to affect OSR plants at flowering, light leaf spot (LLS) continues to increase in terms of incidence, severity and geographical spread.

What are the consequences of not protecting the upper canopy from light leaf spot?

  1. Early stages of light leaf spot begin to emerge
  2. As the plant develops lesions develop on the stem itself. Wind, movement and rainfall are all factors
  3. The flower; infected flowers become malformed and fall off
  4. Light leaf spot spreads from old leaves and stem lesions to pods
  5. Lesions develop on the young pods causing them to distort and prematurely ‘crack’
  6. Essential yield is lost as the pods ‘crack’ and the seeds fall to the ground

Late season light leaf spot

2015 ADAS flowering trial suffered severe late season light leaf spot (85% untreated stems infected with LLS) but only 3% Sclerotinia.

One 2015 ADAS WOSR flowering trial in Rosemaund. Disease in untreated = 3 % Sclerotinia and 85 % stem based LLS recorded post harvest. LLS in untreated in June = 30%. LSD 0.362 Untreated yield = 6.17 t/ha. No LLS recorded in the autumn.


3 years AHDB fungicide performance curves highlight the value of Proline as a cost effective Sclerotinia spray

Spring disease control recommendations


  • Inspect crops for follow up LLS treatment. Spray with Proline275 0.32-0.46 L/ha as soon as LLS is seen pre stem extension or at 15% plants affected at early stem extension
  • If LLS infections remain into flowering then it is essential to use a fungicide with proven activity against this disease, such as Proline275 to help protect the pods.


  • A two-spray protectant approach with Proline275 0.46 L/ha fb 0.32 L/ha is optimal when conditions are conducive to an epidemic (high disease pressure and extended flowering). Proline275 provides the most cost effective and persistent Sclerotinia control.
  • The first Sclerotinia spray aimed at early to mid flowering has the biggest effect on yield. Plan a second Sclerotinia spray 3 weeks later if high pressure persists and flowering is extended.

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Oilseed Rape Diseases

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