The blight fungicide Shirlan is also highly effective against Sclerotinia when used during mid-season canopy complete applications, according to manufacturers Syngenta.

The firm said that the new Shirlan 0.4l/ha higher rate treatment, which received approval last season, gives extended Sclerotinia protection through the potato crop’s flowering period. Excellent foliar blight protection can be achieved through the canopy complete phase when alternated with Revus, it added.

The company’s technical manager, Jon Ogborn, warned that Sclerotinia is an increasing problem in vegetable production areas as the disease thrives on a range of potential crops in the rotation, including carrots, peas, potatoes and oilseed rape.

Meanwhile Scottish agronomy potato specialist Eric Anderson stressed that the warm and humid conditions conducive to blight are also well suited to Sclerotinia development, with each soil born apothecia fruiting body capable of producing eight million acospores, thus creating an enormous infection source.

Anderson advised making an early Shirlan application at the rosette stage to create a coating of fluazinam on the soil surface and minimise Sclerotinia activity, backed up with further foliar applications to protect the crop from infection.

“Our trials have shown the greatest risk is usually 14 to 21 days after row closure, at around the flowering timing. Shirlan application at the 0.4 l/ha - which we would advocate for foliar blight protection - appears to give the greatest opportunity to reduce Sclerotinia infection,” he added.

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