Seed potato growers are being warned about the higher risk of dry rot this season, as the Scottish harvest begins a fortnight ahead of normal. According to the AHDB, the disease is the most important fungal rot of potatoes in Great Britain and planting infected seed next spring can lead to gappy crops. It can be more of a problem on susceptible varieties following an early harvest, warns Stuart Wale, a consultant at Scotland’s Rural College (SRUC).

Poor skin set, warm tubers, and store condensation all increase dry rot risk. He says one way to minimize the risk is by treating the crop with a fungicide when going into storage or at grading.

“Judging the need for treatment should be based on varietal susceptibility to the disease, previous experience of disease on a specific variety, and presence of the disease in the seed from which the crop was grown.”

There are two fungicide options in this situation: imazalil and thiabendazole, which can be used alone or in mixture. Wale points out that Fusarium sulphureum – one pathogen that causes dry rot – has been found to develop resistance to thiabendazole, whereas there has been almost no resistance detected to imazalil.