The service helps growers assess their crops' disease risk level and plan their preventative disease control programme as carrot crops start to become vulnerable to Sclerotinia infection.
Dr Peter Gladders from ADAS Boxworth said: "Sclerotinia germinate when the soil is moist and soil temperatures are 10 degsC and above. So far this year we have barely reached this temperature until the end of April, but in oilseed rape where germination of Sclerotinia has been monitored since mid March we have been finding more germination than last year.
"Carrot growers can pick up the tail-end of the arable crop monitoring, where germination of sclerotia reached more than 54 per cent (at the end of May) in one location and petal tests showed more than 77 per cent Sclerotinia infection. "
The Sclerotinia fungus invades diseased, senescing or decaying leaves of the carrot crop, particularly those in contact with the soil. "Roots are infected via the leaf petioles and through the crown," said Gladders.
"Carrot growers usually start their fungicide applications early, before the canopy closes over, which is sensible because once Sclerotinia is in the crop it is almost impossible to get rid of it.
"Most carrot crops are now planted and the earlier ones have three or four leaves, but most crops have low ground cover so far. Irrigation could stimulate further germination and hence the fungicide programme may need to start in crops sown in April or early May in the next three or four weeks."
Robert Storer, field vegetable product manager for BASF, agreed that timing is key to the successful prevention of Sclerotinia in carrots.
"Signum is a protectant fungicide and it needs to be placed at the base of the plant where infection starts and where old leaves come into contact with the ground," he advised.
"The first Signum spray should be applied before the crop canopy has closed over and the ground is still visible. A closed canopy creates the right conditions for further infection and shields the base of the plant from fungicide sprays."
Signum is fully approved in carrots and provides broad-spectrum disease control of Sclerotinia, Alternaria and powdery mildew. Trials data showed that Signum also gave good control of diseases responsible for the loss of yield and quality in carrots.
Storer added that trials showed that Signum was an effective option. "In ADAS trials Signum gave 58 per cent control of Sclerotinia, compared with just five per cent for azoxystrobin and 28 per cent for tebuconazole. For Alternaria, Signum reduced infection levels to 19 per cent from 55 per cent, with azoxystrobin reducing infection down to 30 per cent and tebuconazole to 28 per cent."