The whole potato industry must work together to eliminate CIPC residue anomalies or the sprout suppressant will be lost, visitors to the recent Potato Council storage day at G H Chennells Farms in Lincolnshire were told.

New limits on both total CIPC applications and residues were now in place, after the re-registration process. But the Advisory Committee on Pesticides had asked for further action on residues, said Mike Storey, Potato Council research and development director.

“We won’t get a second chance,” he said. “Random sampling by the authorities has shown that there’s potential to exceed the 10mg/kg maximum residue limit, even when applications have been made according to best practice.”

As a result, the CIPC Stewardship Group was formed in January, with Dr Storey appointed as chairman. Members include researchers, grower groups, packers, processors and agrochemical companies.

“We’ve been tasked with coming up with an action plan which meets the requirements for reducing these residue anomalies. We have to demonstrate that we are a responsible industry.”

Not only is there an MRL of 10mg/kg, there are also limits on applications. Potatoes treated with more than 36g of active ingredient per tonne should only be used for commercial processing, with an upper limit of 63.75g ai/t.

The five-point action plan being developed by the stewardship group includes the use of monitoring and the imposition of controls, including training, equipment testing, protocols and a code of practice, Dr Storey said.

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Monitoring was likely to include voluntary and anonymous submission of residues data by processors and packers, he confirmed.

All operators using fogging equipment would have to be qualified to PA1 and PA9 standards. “We hope to have this in place by the end of 2008.”

Annual testing would be introduced to ensure fogging machines were running efficiently, he added. “This is similar to what’s already done with field sprayers.”

Potato stores would be part of the action plan, with definitions of criteria which make a store good for fogging with low rates agreed. “We’ll also be defining the type of stores that require excessive product to control sprouting, such as older buildings with poor circulation or no fans.”

Crop Assurance protocols would promote good application practice and a code of practice would be developed to promote the best techniques for CIPC application, he said.

“It’s not possible to use CIPC with no detectable residues, but we can learn to use it more efficiently and effectively,” said Dr Storey. “The correct timing of the first application is critical.”

CIPC Information

  • Maximum residue level of 10mg/kg
  • Processing or peeling – total application of 63.75g ai/t
  • Fresh market – total application of 36g ai/t

CIPC application techniques

Box stores are the most challenging for achieving even CIPC distribution, according to the Potato Council’s Adrian Briddon.
“We’ve developed a new application procedure for bulk stores which means that the limits won’t be a problem. But box stores aren’t so straightforward.”
For box stores, Mr Briddon suggested applying CIPC via a plenum, or alleyway. “This helps because the fog can’t rise up into the roof space immediately. It has to move through the boxes.”
Box stacking patterns might help, he acknowledged. “There’s more work to be done here.”
Conventional application of CIPC could result in uneven distribution of the treatment, earlier regrowth and the need for further applications, he pointed out.
“In a bulk store, a better procedure is to use low-speed recirculation of the fog through the bulk piles. The fog is circulated around in a balanced system.”
The airflow into lateral ducts had to be balanced, he advised. “This can take a bit of effort, but it’s worth the time. Laterals closest to the fan will need closing down to about 30% of their normal size.”
New guidelines, Improving the Use of CIPC in Bulk Stores, had been produced by Potato Council, containing more detail and advice, he said.
The most common mistake with fogging was the timing of the first application, he added. “Many initial treatments are made too late. It’s important to treat potatoes before the eyes are open. There is a slight reduction in efficacy in warm conditions, but you still must treat.”
Soil created a physical barrier, so the amount taken into store should be minimised, he added.