Potatoes are likely to suffer storage rot this season due to climatic issues, is the stark warning from experts at the Central Science Laboratory (CSL), who have been monitoring disease levels during the season.

The lab is urging growers to check the health status of tubers prior to storage, and ensure they are not building up trouble for themselves by retaining high-risk lots.

The high incidence of potato blight coupled with high inoculum loads of soft rot bacteria, resulting from waterlogged conditions, presents a particular storage risk.

But the combination of tuber blight and soft rot can have a much higher impact than either disease alone, even in well managed stores, because infection of tubers by the blight fungus creates a microclimate suitable for entry and multiplication of the soft rot bacteria, and this leads to ‘hot spots’ within the stored crop from which rotting pathogens can multiply and spread.

CSL expert Dr John Elphinstone said: “It is sensible to sample crops prior to harvest in order to assess the level of tuber blight and their soft rot potential. This can be done by sampling and washing 300 tubers at random from the field, incubating them in a ‘hot box’ at 18-25oC and observing disease development over a period of one week. Alternatively, growers could consider sending samples for laboratory analysis to accurately determine infection levels.

“Once test results are known, potato crops can be graded in terms of storage risk. High-risk areas of fields, for example waterlogged spots or tramlines, can also be identified and stored separately, or sent straight to market or processing.”

Dr Elphinstone recommends that if crops at risk must be stored, dry them as quickly as possible with adequate ventilation, and cool them as fast as possible. Continued monitoring and sampling throughout the storage period can then provide reassurance that the crop is storing well, or give an early warning if it needs to exit the stores earlier than planned.

“This is a challenging season in many ways,” added Dr Elphinstone. “Growers need to make certain that the market potential of harvested crops is not spoiled through storage of tubers which are likely to rot.”

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