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According to BASF/ADAS Sclerotinia Monitor, sclerotia germination at Cambridgeshire has increased, with 12% of sclerotia producing small apothecia. Germination has increased to 15% in Lincolnshire and to 3% in Devon. Growers and agronomists are advised to keep a close eye on the situation by logging onto www.totaloilseedcare.co.uk for weekly updates and be ready to act.

In addition to the Sclerotinia Monitor, growers should also keep an eye on local conditions, advises Clare Tucker of BASF.  "Soil temperatures above 10°C have been shown to initiate sclerotia germination and night time temperatures above 7°C to initiate infection of oilseed rape plants by air-borne spores. It could easily be a critical year for Sclerotinia and a robust two-spray protective programme will be needed."

"Crops are at highest risk when sclerotia germination is synchronised with early flowering, but new field trials observations have shown petal stick doesn't always have to occur as an infection risk factor. Recent trials observations show that older leaves in the lower canopy and leaves in the central part of the canopy are less waxy than newly emerged leaves and so are more susceptible to infection. Leaf weathering has been shown to increase crop susceptibility and can replace the necessity of petal stick as an infection risk factor."

Clare advises that forward rape crops (which have a Green Area Index of more than 2 measured at the start of stem extension) will benefit from a PGR fungicide that can also act as the first spray for Sclerotinia.  "Applied at mid-stem extension Sunorg Pro will reduce apical dominance, so increasing light penetration to the pod canopy as well as increasing rooting, important to help the crop through dry conditions. It also reduces lodging by 30% which is a major cost saver in terms of yield and harvesting difficulties. Crops in 2012 are generally too far forward and need an effective PGR at mid stem extension. This should then be followed up around mid to end of April with an early flowering spray of Filan or Compass. If the risk remains high, a third spray could be applied 3 to 4 weeks later. Two Filan sprays can be made to a crop. For good resistance management the second Filan spray should be partnered with a fungicide with an alternative mode of action, such as metconazole or mbc."

For average sized crops, which were greater than GAI of 1 at stem extension, Clare Tucker advises an application of metconazole at yellow bud which will also protect against early Sclerotinia infections. "Sprays at this time reach the lower canopy and provide direct protection of the main stem and leaves against Sclerotinia infection, as has been demonstrated in spray coverage experiments. This spray will also help the flowering sprays which cannot provide full coverage of the lower canopy by opening up the canopy. Once again this early spray should be followed by a mid-flowering treatment at the start of petal fall, around early May, with Filan and Compass providing excellent levels of control plus yield increases."

She points out that both Filan and Compass can be tank-mixed with a pyrethroid at flowering.

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."

The Sclerotinia Monitoring service monitors 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 from 16th March until the beginning of June. 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.