According to the Potato Council, growers have been reporting that small pockets of rot are developing into bigger problems. Blight and watery wound rot have been the main causes but cases of bacterial soft rot have also been widespread.
About 3.5 to 4 million tonnes of the British potato crop is stored each year, worth more than £400 million. About half the crop is destined for the fresh pre-pack market, the rest for processing.
"This is not a winter to sit back and relax, with the crop safely gathered in," said Adrian Cunnington, operations manager of the Potato Council's Sutton Bridge Experimental Unit.
"Black dot levels are high, affecting skin finish in pre-pack crops, especially those harvested later in the season. Fry colour is also a cause of worry in processing material, with high levels of variability making it difficult to appraise crops' suitability for market."
Cunnington has advised store managers to be alert for any changes in the crop in store, such as localised hot spots or the appearance of condensation.
"Inspections should be made at least twice a week, with a minimum of monthly assessment of critical market criteria, such as skin finish or fry colour. This will help to provide up-to-date information on the status of each crop and, subject to market conditions, offer the opportunity to place crops if things don't go to plan," he said. "There is no financial sense in keeping crops in store for the sake of it."
- Store managers are also reminded that new rates are in force for the sprout suppressant chlorpropham (CIPC). Up to 36g of CIPC per tonne of treated crop can be applied over a season to potatoes destined for the fresh market. The maximum dose for processed potatoes, including those used for peeling and fish and chip shops, is 63.75g/tonne. The Maximum Residue Level (MRL) is 10mg/kg.