Chemical company BASF and rural consultancy Adas sponsored a Sclerotinia monitoring system that has been set up to help carrot growers assess their disease risk and plan an effective control programme.

Adas Boxworth’s Dr Peter Gladders said: “The Sclerotinia pathogen survives in the soil as resting bodies or sclerotia, which can remain viable for up to 10 years, and germinate when conditions are favourable. This is when soil is moist and temperatures are between 5°C and 25°C. The fungus then invades diseased, senescing or decaying leaves, particularly those in contact with moist soils. Roots are infected via the leaf petioles and through the crown.”

The Sclerotinia monitoring system gauges the germination pattern of sclerotia and monitors germination weekly from June to August. As sclerotia provides the source of infection within the carrot crop, this indicates the extent of the Sclerotinia risk and the need for fungicide treatment.

“Growers should keep checking the published information on the internet and be ready to take action,” said Gladders.

Sclerotinia has become a much more widespread and serious disease in many crops, including carrots, brassicas, peas and beans. “As a consequence, carrot growers are starting their programmes earlier, and using more robust fungicides right from the start,” said Gladders.

“It is particularly important to get the first fungicide spray on early before the foliage has a chance to close over and starts to senesce. Once the disease is in the crop, it is almost impossible to get rid of it.”

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