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Managing sclerotinia stem rot in canola
Summary of recommended strategies:
- Use good quality seed that is free of sclerotia.
- Avoid sowing canola next to paddocks that were infected with Sclerotinia in the previous three years.
- Check for Sclerotinia symptoms in broadleaf crops if considering sowing canola into the same paddock the following year.
- Preventative strategic sprays of foliar fungicides at early to mid flowering. Fungicides should only be considered for very high yielding crops in districts prone to Sclerotinia.
The disease sclerotinia stem rot is caused by the fungus Sclerotinia sclerotiorum, which can occur on many common broadleaf crop and weed species, particularly canola and lupins. Cereal crops and grass weeds do not host the disease.
The fungus can be soil-borne or carried with seed. In Australia, the disease is highly sporadic requiring specific environmental conditions to develop and disease incidence can vary greatly from year to year, but is most damaging with prolonged humid or wet conditions during flowering.
The sporadic nature and inconsistent relationship between the level of stem infection and yield loss make it difficult to reliably make foliar fungicide application decisions. Several forecasting tools developed overseas have been evaluated in Australia, but have been found to be inappropriate due to differences in climate and length of flowering. Yield loss is often difficult to predict,
but can be up to 24% under Australian conditions, depending on the percentage of plants infected and the crop growth stage when infection occurs.
Current management options before sowing are limited to sowing clean seed, isolating canola from last year’s infected paddocks, and crop rotation. The use of foliar fungicides at flowering is the only management option post-sowing.
Trent Potter, Steve Marcroft, Don McCaffery and Felicity Pritchard for reviewing and technical editing of this Factsheet. Printing for this publication was funded through the Oilseeds Industry Development Officer and Better Oilseeds projects of the Grains Research and Development Corporation and the Australian Oilseeds Federation.
This publication may be of assistance to you but the Canola Association of Australia, Grains Research and Development Corporation and the authors do not guarantee that the publication is without flaw of any kind or is wholly appropriate for your particular purposes and therefore disclaim all liability for any error, loss or other consequence which may arise from you relying on any information in this publication. The information contained in this publication is based on knowledge and understanding at the time of writing (August 2008). However, because of advances in knowledge, users are reminded of the need to ensure that information upon which they rely is up to date and to check currency of the information.