A new potato industry initiative launched last month aims to prevent any further cases of a key sprout suppressant being found in fresh and processed potatoes, thus securing its future use.
Chlorpropham is a vital tool for the potato industry in preventing sprouting, as there are no real alternatives. Research shows the use of CIPC vapour is not viable and other actives, such as spearmint oil, are viewed more as helping reduce CIPC use rather than being a replacement.
The Advisory Committee on Pesticides initially raised concerns over CIPC (chlorpropham) residues back in 2007, which prompted the industry to act with the implementation of a five-point plan in the past five years.
This included the setting up of the Potato Industry CIPC Stewardship group, a considerable investment of £2.23m by the Potato Council into research and promotion of best practice based on the research results.
“These measures have resulted in changes in application and growers have a much better understanding of controls compared with five years ago,” says Mike Storey, chairman of the stewardship group.
But despite this huge progress, there have been seven exceedances in the five years since the group was established, exceeding the maximum residue limit of 10mg/kg.
“This is seven too many and the stewardship needs to continue,” says Dr Storey.
Back in January, the group submitted a report and are awaiting the outcome of the ACP, which will dictate the future of CIPC. But rather than wait, the industry is being proactive in launching the “Be CIPC Compliant” campaign with new measures ahead of the new storage season.
Looking at the seven exceedances, there are common themes that have helped shape the new measures based on best practice and research. Dr Storey highlights that most involved potatoes for the fresh sector and all but one involved box stores.
“But that doesn’t mean we should become complacent with bulk stores holding potatoes for processing,” he adds.
There are new additional recommendations on the label, the first being that growers should apply it early within three weeks of harvest, or at the earliest occasion thereafter, even in the absence of signs of breaking dormancy.
In cold stores, which account for 40% of stores, CIPC should only be used once and carried out before the crop falls below 7C. Adrian Cunnington, head of Sutton Bridge Crop Storage Research, explains that evidence shows the chlorpropham degradation rate in cold stores is slower.
“You don’t get effective movement at lower temperatures,” he says.
It is the vapour that gives sprout control and its concentration in air is strongly related to temperature, explained Potato Council technologist Adrian Briddon. He believes this is the reason for the sluggish responses. “The air can’t carry enough CIPC vapour, so you see hot spots for longer in cold stores.”
“I would also advise against using a full rate dose in cold stores,” he says.
Before treating cold stores, the ventilation system needs managing to stores time to adjust, says Mr Cunnington. “Fans should re-circulate store air for at least six hours before application without cooling, to ensure there is an even temperature in the store.”
Dr Cunnington advises more forward planning. “It needs good communication between contractor and grower, so they know when the fogger is coming and prepare beforehand.”
Positive ventilation is recommended, but there are still many box stores that use an overthrow (non-positive) ventilation system, says Mr Briddon. Air is thrown over the top of the stacks and returns back to the intake between or around boxes – not necessarily through the crop.
“Work has shown that in these arrangements, you can have some of the top boxes with CIPC concentrations above 10mg/kg while other boxes in other areas of the store get little, so no effective sprout suppression. Therefore, store managers tend to apply more, thus increasing the risk.”
In these stores, Mr Briddon suggests modifying the stacking pattern and creating a covered plenum, which then acts as the main duct with the pallet apertures acting as lateral ducts.
“You see a much narrower range of concentrations across the boxes. It’s not a long-term fix but is a lot safer,” says Mr Briddon.
Checklist and planning
Another key change this autumn is that the CIPC store checklist, carried out before filling the store, is now required under the Red Tractor scheme, having previously been voluntary. Failure will result in failing Red Tractor compliance.
Dr Story explains that it helps encourage farmers to consider the stacking pattern and where the fog is introduced before loading potatoes into store.
NAAC contractors are a key part of the initiative, as they can only apply in stores that pass the CIPC Store checklist. They apply the treatment on the recommendation of a BASIS-qualified adviser and equipment must be tested, and they hold the appropriate qualifications.
“However, the store owner should agree rates with contractors, as they are responsible for CIPC use and ensuring concentrations in potatoes don’t exceed the maximum limit,” says Mr Briddon.
Application limits applied are currently 36g/t of CIPC for fresh and 63.5g/t for processing potatoes. However, Dr Storey says it is being reviewed and expects it to be 36g/t for both from 2017.
The industry could also see tighter restrictions for higher risk stores, says Mr Briddon, namely cold and non-positively ventilated stores. “New stores needing CIPC must have positive ventilation.”
What growers need to do checklist
1 Review the need for CIPC
2 Review store
3 Review strategy with an NAAC contractor
• Initial early application
Bulk stores and box stores with positive ventilation
• Fit inverters to fans
Box stores without positive ventilation
• Prevent fog rising into headspace
• Limit does in “packing” stores
Be CIPC compliant
The new campaign is targeted at all the whole industry, rather than those who are not getting it right.
“We want to keep it in the front of growers’ minds,” says Sharon Hall, who is also part of the stewardship group.
“We also want to help communicate to legislators what we are doing.”
She adds that the group has secured a commitment from the supply chain with both the potato processors association and fresh potato suppliers association committed to only source potatoes from CIPC compliant stores.
“We are now looking to get commitment from other areas of the food chain.”
The new website has resources on best practice, including the latest guidance, research being carried out at Sutton Bridge Crop Storage Research and CIPC store checklists and news.
The Potato Council is also running a series of road shows in the coming weeks and will also use the press, text alerts and industry newsletters to target growers.