ADAS and BASF's web-based Sclerotinia monitoring service goes live in March for the 2012 season, in what is a potentially early disease pressure year. The service, which is free, can be accessed from w/c 12th March onwards at www.totaloilseedcare.co.uk and will run for a twelve week period.

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Dr. Peter Gladders of ADAS believes that, if the weather continues warm, oilseed rape crops will continue advancing and could be flowering by early April.  "In the past we have seen the first germination of sclerotia in late March and we might see that again this year. Certainly most rape crops are already large and well advanced this spring. If they continue that way, then the risk of Sclerotinia will be high if crops lodge. So the priority will be to manage nitrogen sensibly and use plant growth regulating fungicides such as metconazole in order to keep the crop standing as well as for canopy management. Crops with high GAI will need a robust PGR programme this year. The early applications of metaconazole will also start off the Sclerotinia control programme."

The Sclerotinia Monitoring service allows growers to monitor germination of the pathogen's sclerotia at six sites in Cambridgeshire, Yorkshire, Herefordshire, Lincolnshire, Kent and Devon. Germination assessments are made each week for 12 weeks and results are updated every Friday, starting on 16th March. Each site is further supported by petal tests at first flower, early flower and mid-flower, which will help establish disease pressure from air-borne spores.

Sclerotia can remain viable for many years

Dr. Gladders reports that last year Sclerotinia incidence was generally low, mainly due to the dry conditions restricting sclerotial germination. "The worst affected region last year was the South West which fitted in well with sclerotial germination results from the Monitoring service. The petal tests showed a low background level of Sclerotinia, even in the dry areas of eastern England. But I would warn growers that there is still a significant level of viable inoculum in the soil from the two heavy infection years of 2007 and 2008. Sclerotia can remain viable in the soil for many years, if buried. As rape is being grown in tight rotations, many fields have sclerotinia in the soil. You don’t need many sclerotia to create an epidemic – just 2 sclerotia per square metre to start an epidemic. The high price of oilseed rape at this time makes the crop well worth protecting, especially as yields of affected plants can be halved as a consequence of premature ripening."

Monitor soil temperatures

Dr. Gladders advises growers and advisors to review the Sclerotinia monitoring reports every week from now on. "Farmers can monitor their own soil temperatures and compare this with the sclerotia depot system. A soil temperature of 10°C is needed for sclerotia to germinate actively. Rape crops are at highest risk when sclerotial germination synchronises with early flowering. Spores infect the plant when minimum temperatures are above 7°C and there are long periods of high humidity."

Peter Gladders is convinced that last year record yields of oilseed rape show that modern agronomy, with attention to detail throughout, really works. "This year is no different. Crop values are high and the potential to optimise yield through planned canopy management as well as through protecting the crop from disease remains important."

Will Reyer adds that, because fungicides are mainly protectant, it is important to understand disease risk and when the disease is likely to come into the crop. "Knowing this information puts you in a better position to time fungicide applications correctly, in advance of disease and before any significant petal fall, hence the need for disease monitoring. BASF advise growers to start their programme with an early Sunorg Pro for canopy optimisation as well as early disease control and then follow up with a early to mid-flower fungicide treatment of either Filan (boscalid) or Compass (thiophanate-methyl and iprodione)."