Scottish potato growers have been warned to keep a close eye on tuber condition and plan how they will unload stores to satisfy customer requirements. As store unloading gets underway, careful attention must be paid to withdrawal periods when using sprout suppressants, notes managing director of North Berwick-based Crop Chemicals Jim Rennie.

“Now is the time to think about how you will manage unloading your stores to satisfy contracts and make the most of any opportunities that arise,” he advises. “In the past growers have been unable to benefit from early and short-notice contracts because their stock may be restricted from unloading, following a chlorpropham (CIPC) application. Only those with extensive storage facilities and the ability to move potatoes into untreated sheds have managed to maintain a consistent unloading pattern.”

But a new CIPC product, Luxan's Gro-Stop 100, is set to ease some of these management headaches. It can be applied to stored potatoes as little as two days prior to unloading the store. This allows growers to supply an order for either the fresh or processed market at short notice, and yet still maintain maximum protection from sprouting.

“This is a substantial reduction on the usual 28-day unloading restriction. It builds in a lot more flexibility for the average grower, and we reckon this will have significant benefits for how they manage their contracts,” explains Mr Rennie.

Most stored potatoes are in good condition despite the very wet weather in August last year, he reports. “But vigilance is needed - there are more soft rots and pink rots than we've seen for a while. These are the problems growers must watch out for, and they will also have an impact on chlorpropham (CIPC) applications.”

Rots create hot spots in store that can affect dormancy. “You also need good ventilation for CIPC applications, and heat build-up caused by rots will affect this. You can also find problems with condensation which leads to poor spread of CIPC around the store.”

This means a well-formulated material is essential, adds Mr Rennie. “We've found Gro-Stop gives a good, even distribution around the store. This, and the low dose regime(1) ensures residues are kept low.