As the potato storage season looms, growers are being urged to make best use of CIPC to safeguard its future. Louise Impey finds out how one farmer has reduced his reliance on the sprout suppressant while meeting tight market requirements

Lincolnshire potato grower Andrew Chennells has successfully reduced chlorpropham use in bulk stores, but admits that there’s still work to be done before the same is true in the business’s box stores.

Mr Chennells, who works closely with the Potato Council on storage research, grows all his potatoes on contract for a major crisp manufacturer, so has to meet particular storage requirements.

“Our potatoes have to be stored between 8C and 10C, which is warmer than those destined for pre-pack markets,” he explains. “As a result, we have more issues with sprouting control, as warmth shortens the dormancy period.”

In addition, the storage period can run from September right through until the end of June, making repeated CIPC applications necessary. But agreed legal limits on CIPC use have to be adhered to, points out Mr Chennells, who believes that further reductions will be imposed on UK growers before too long.

“The maximum dose allowed on potatoes destined for processing is 63.75g/t,” he says. “But for the rest of Europe it is 36g/t. It’s hard to believe that we’ll be allowed to carry on using twice as much as other growers for much longer.”

At GH Chennells, there are two bulk stores and two box stores. Experience has shown that sprouting can be managed adequately in the box stores with 63g/t of CIPC, but bulk store use has been cut down to 28g/t.

“Depending on the season, we use between 28 and 42g/t in the bulk stores. So there’s been real progress. Just five years ago, when there were few limitations on CIPC, we were using 90g/t.”

Getting a more even distribution of CIPC has been key to his success. “We used to shut the whole store down and let the CIPC find its way round the potatoes. But that’s changed and we now run the fans at very low speeds, so that the CIPC is pushed through by low volumes of air.

“It prevents the problem of under and over-dosing, which was always traditionally associated with CIPC application.”

Potato Council-funded research is behind this change of approach, reports Mr Chennells. “In the USA, low fan speeds have been used to distribute CIPC for some time. And they’ve been applying less than we have in the UK, without compromising sprouting control.

“That’s been investigated by the Potato Council. By fitting variable frequency drives, we’ve been able to use low fan speeds to achieve the same result.”

In the box stores, he has to use 63g/t. “The type of store you have is a big issue. The overhead throw box stores aren’t ideal when it come to CIPC, but we are stuck with them for a while yet. Fortunately the Potato Council is midway through a research project which should help.”

Technologist Adrian Briddon from Sutton Bridge Crop Storage Research confirms that work is on-going. “We’ve had some encouraging results in box stores with positive ventiliation, which seems to help with evenness of supply. It’s all about getting enough CIPC to the least accessible potatoes, without overdosing the others.”

The introduction of a store self-audit this season doesn’t alarm Mr Chennells. “All of our stores are relatively modern, so we’re confident that they meet the scheme’s requirements.”

He adds that the reduction in CIPC use has also been a considerable cost-saving to the business.

“The difference between six doses at £5.50/t in a box store and two doses at £1.80/t in a bulk store is £3.70/t per season,” he calculates. “So with 6000t of potatoes in a store, that’s a saving of £22,200. With 9000t, it’s worth £33,300.”

Application Advice

Don’t delay CIPC use, as the sprout suppressant should be applied while the tubers are still dormant, advises Adrian Briddon.

“Early use, before any sprouting occurs, is the best way of ensuring that limits are not exceeded,” he adds.

The belief that CIPC shouldn’t be applied until the temperature is below 10C is wrong, he stresses. “Sprouting will take place earlier if it’s warm.”

CIPC should be applied as soon as curing is complete, which is within two weeks of lifting, he ends. “Programmes need to be front heavy to pre-empt sprout growth.”