Tackling stem rot (Sclerotinia) in OSR

The Home Grown Cereals Authority (HGCA) in the UK has published the latest thinking on how best to combat the threat of sclerotina in oilseed rape (OSR), using targeted fungicide programmes. Sclerotinia stem rot is usually the most problematic disease at flowering and can cause up to 50% yield loss in affected plants.

The advice now available reflects the work that has been carried out on behalf of the HGCA, looking at disease control and yield responses at two sites from 2010-2013. The key findings are:

  • Fungicide timing is vitally important for good control as products are protectants and have little or no curative activity;
  • Product and dose effects can be significant on disease development when sclerotinia levels are low and high. Yield responses will depend on the timing of onset and disease development in the crop;
  • The optimum timing for a single spray is usually just before mid-flowering on the main raceme;
  • Treatments provide good control for about three weeks. Two sprays may therefore be required to protect crops at high risk sites throughout the flowering period;
  • Fungicides differ in their physiological effects on the crop and this should be considered when selecting products (e.g. is growth regulation required?);
  • Strategies are required to minimise the risks of selecting fungicide resistant strains of sclerotinia and other pathogens; and,
  • Do not use sclerotinia products containing single active ingredients more than once on their own. Use mixtures, co-formulations or products with a different mode of action.

Teagasc is reporting that Irish Oilseed rape crops have grown strongly over the past three weeks. As of a week ago all crops were at the stage of the first flowers appearing. Disease levels have increased with Light Leaf Spot reported widely. Pollen beetle is evident in some crops across the country. Significantly, Teagasc is advising that growers should treat fields at risk from sclerotinia over the coming weeks (at the start of petal fall).

 

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