The BASF- and ADAS-sponsored Sclerotinia monitoring system for carrot growers is indicating that the first fungicide treatments will likely be required where main crops are near to achieving full ground cover.

Dr Peter Gladders from ADAS Boxworth said that, although Sclerotinia germination is lower than usual at the reference sites in Norfolk and Nottinghamshire so far, intensive irrigation or more rainfall would allow sclerotia to germinate in carrot crops.

He said: “Main crops sown in late April now at the 7 to 8 leaf stage and so these crops have almost achieved complete ground cover in the beds which will favour sclerotinia activity as soils remain moist. This is the time to apply the first fungicide just before canopy closure.”

Gladders points out that the recent hot dry weather is inhibiting sclerotial germination, but that irrigation or rainfall could encourage germination when there are moist conditions at the soil surface.

He added: “Any area with irrigation or significant rainfall in last few weeks could be at higher risk than the monitored locations. Crops should be inspected regularly not just for Sclerotinia but also for Alternaria leaf blight, Cercospora leaf blight and powdery mildew.”

The monitoring system monitors patterns of germination each week and indicates the extent of disease risk and the need for fungicide treatment.