Extra disease monitoring required for Northern rape growers

Oilseed rape farmers in the North know that their crops are at high risk from Sclerotinia and are prepared to spray almost routinely at the early to mid flowering stage. BASF, SAC and CSC are co-operating in an extra predictive modelling system to gauge the level of risk as the season progresses, explains Plant Pathologist, Dr. Simon Oxley of SAC.

"For the first time we have a site in Scotland which monitors germination of the pathogen's resting stage, the sclerotia, buried in fields of winter rape. Germination activity at this site and five other sites across the UK is reported weekly on the website www.totaloilseedcare.co.uk. In mid-April crops were at early bud to early flowering, but no sclerotia had germinated as yet. In addition, we also have a weather-based predictive system using Plant Plus designed to assess the length of time that the crop is at risk." says Dr. Oxley.

Normally the Sclerotinia treatment, such as Filan, is applied at early to mid flower to protect the petals. Growers are being advised this year to make sure that they apply their first spray in appropriate water volumes. "Last year water volumes of 120-180 litres per hectare covered the petals, but resulted in poor penetration and coverage further down the plant. This year it is important to use a higher volume, as stated on the label, to ensure good coverage lower down."

Simon explains that last year conditions were such that the disease germinated later and over a long period of time, well into June and July.

In addition the weather in June and July was cold and windy and this damaged the crop, leading to primary Sclerotinia infections via damaged leaves, not the petals as is the norm. So crops were treated early but infected late. The monitoring systems will answer the question; will the disease have such an extended window as last year?

"Sclerotinia continues to be a problem in the North. In this part of the country, crop rotations tend to be tight (for instance barley, rape, barley, rape) and include many crops such as oilseed rape and potatoes that are susceptible to this disease. After last year, there will undoubtedly be a large reservoir of sclerotia in the soil ready to attack susceptible crops, when the weather comes right. Fungicides treatments are not the entire answer and growers are advised to introduce some cultural methods of control into their planning," suggest Simon.

In terms of treatments, Filan is the most widely use fungicide for Sclerotinia. "We are becoming reliant on triazoles for Light leaf spot control. A triazole is usually applied against Light leaf spot in the autumn, another at stem extension and potentially a third at flowering. This puts too much pressure on Light leaf spot populations with regard to resistance. It is important to give the crop a break from triazoles and use something different and effective such as boscalid."

"Filan is the proven Sclerotinia fungicide, giving reliable and consistent protection against this damaging disease as well as broad-spectrum activity against Alternaria and Botrytis. It has greater persistence that allows application at early flowering. It can also be tank-mixed with a pyrethroid insecticide for pest control, unlike triazole fungicides. Filan is recommended at a dose rate of 0.5 kg/ha at early to full flowering before disease symptoms are visible." says Diane Heath, BASF Oilseed Rape Product Manager.