22 October 1999

Variable crops mean special care vital in store strategy

By Andrew Swallow

VARIABLE condition of potato crops this autumn means growers should take extra care loading stores, say experts.

Higher levels of disease are present on many samples, and plans must be made to handle each field, or even parts of fields, according to disease risk.

"Growers must use crop intelligence to build a store strategy," says Greenvale AP technical director Simon Bowen. "Levels of tuber rotting are higher than have been seen for a number of years, and the worst thing to do is assume all the crop is the same."

The best samples should be lifted first, so these are at the back of stores. Any areas at risk from tuber blight or blackleg should be put aside, and ideally not stored at all.

ADAS national potato specialist Denis Buckley adds that growers shouldnt attempt storing potatoes that have been flooded. "Theyll be starting to rot," he says.

Less tuber blight than might have been expected is thanks to thorough fungicide programmes. But pink rot is widespread on tubers, and hard to spot, he warns.

"Infected tubers look dull and wet, and develop a pink tinge on the flesh when cut open. Theres a real danger of bacterial rots coming in on the back of pink rot. Stores need to be ventilated well – drying is the main thing."

Skin finish snags

Skin finish is posing substantial problems for some growers, with surprising levels of common scab.

"Theres more than we would expect and I havent a clue why. There was plenty of rain during tuber initiation and irrigation could cope with any soil moisture deficits, yet good clean samples are hard to find."

That is echoed by NIABs Pete Saunders. "Skin quality is all over the place this year. Weve got to put our thinking caps on to find out why."

Significant levels of black dot and silver scurf are also present on tubers. For undamaged tubers growers should consider curtailing curing periods to limit the development of such diseases, suggests Mr Bowen.

"Damaged tubers need 8-10 days at 10-12C to cure wounds. But that is a window for black-dot and silver scurf to develop and can be cut down. Now lifting conditions have improved, growers would do well to slow down and take things more gently to reduce damage."

Cooling the store from 14C to 8C can take a week in any case, and large stores may take three to four weeks to load, he adds.

"Growers should consider the option of starting to pull down the temperature before the store is full. Smaller stores really come into their own in these kind of conditions," he says.

Lower field temperatures are increasing the risk of bruising, adding to the case for more care with handling.

"We often say to growers if it is a frosty night dont start lifting until lunchtime. Allowing the outside of tubers to warm up two or three degrees can have a significant effect."