With potato growers having to cope with a ban on the use of CIPC effective from this autumn, AHDB is offering free one-to-one potato store visits via its new Storage Network to help businesses improve their storage and prepare for loss of the chemical.
At JSR Farms in East Yorkshire, potato storage is a key part of the business, with the company storing its own potatoes as well as those from other farms.
JSR Farms grows 200 hectares of potatoes, 90% of which are for seed and 10% for the prepack market on contract for R.S. Cockerill.
At JSR’s Southburn facility on the Yorkshire Wolds, it stores 1,500 tonnes of processing potatoes destined for Kolak and Seabrook plus 1,000t of packing potatoes and 2,200t of seed potatoes. It also stores 2,800t and 1,000t of processing potatoes at two other sites.
Managed by Adrian Cunnington, head of crop storage research, the AHDB Storage Network visit, Sutton Bridge, covered all the JSR sites.
John Smith, JSR Farms storage and produce manager, says all the stores at Southburn are ambient ventilated, except the seed store which has refrigeration.
Stores 1 and 2 are used for processing crops treated in the field with maleic hydrazide to give a base level of sprout control. The stores are of metal and styrofoam construction, under the same roof, with Store 1 holding Opal and Store 2 allocated to Taurus, both crisping varieties.
Potatoes normally remain in the store until May and sometimes early June. Both receive two applications of CIPC for sprout control.
“The cooling is ambient with automated control and the target store temperature is 8.4-8.9degC,” says Mr Smith.
Currently, Mr Smith plans to use spearmint oil in 2020/2021, instead of the now-banned CIPC. He plans to overspray Stores 1 and 2 with 25mm polyurethane to help seal the store and cover the existing styrofoam panels.
Mr Cunnington says: “There is a level of uncertainty over whether some stores can be treated with mint oil if they are insulated with styrofoam. Some contractors are not happy to treat them because the liquid version of the chemical can damage the insulation.”
He adds it is also important to seal louvres when applying volatile chemicals such as spearmint oil.
“When louvres are leaky they are letting uncontrolled air in. The new chemicals are quite volatile and if you don’t seal them you could get leakage of air through the store which will drive the chemical out.”
He advises store managers to look at stores and decide whether they need to make changes to louvres and vents.
“Brushes on the end of louvres in Stores 1 and 2 mean they seal quite well.”
When applying spearmint oil, Mr Cunnington suggests treating the two stores separately as there is a dividing wall in the roof space.
“If you need to treat one store at the end of next season and not the other, you can keep the chemical where the potatoes are, which will aid control. Volatile treatments do not work well in big spaces where there are no potatoes. It needs a focused application.”
Stores 1 and 2 contain an old fridge unit, no longer used, and Mr Smith asked if he should take out.
Mr Cunnington says: “No, hang on to it as in the future we may see a move to storing at cooler temperatures and may need to use more refrigeration in preference to ambient air so we can cut down on air exchange.
“Over the coming years we expect a change to varieties which will be more cold temperature tolerant as we will not be able to control sprouting to the same level as with CIPC.”
In general, Stores 1 and 2 are performing well. Mr Cunnington praises the use of temperature probes at the top and bottom of the stack to measure temperature gradients.
“This is a good store. The main issue is the insulation will need an overspray. Alternatives to CIPC such as mint oil and DMN are four times as expensive and we want to keep hold of them.”
Chemical control is not the only way forward. While it is almost essential for processing crops, those with fresh market and seed potato stores can take more of an integrated crop management approach.
Store 3 at the Southburn facility is a 1,000t box store for prepack potatoes with metal cladding insulated with spray foam.
The potatoes in this store are not treated with a sprout suppressant, says Mr Smith.
“Last year, we managed to store them just using ambient air and sell them before Christmas.”
Mr Cunnington says: “There is a fridge system in the store but it is not really big enough so the store is only being used for short-term storage, which offers a limited return. If this was to be upgraded to store for longer, money would need to be spent on a new fridge unit.
“This would provide JSR with a future-proofed capability to store for the long-term fresh market and, if the air distribution was enhanced a little, would not need to involve the use of chemical treatments.”
Store 4 is a seed store and therefore is also chemical-free. It is of composite panel construction with fireproof insulation injected into the middle of the steel panels.
Mr Cunnington says: “Most of these stores have been put up in the last 15-20 years. From a cleanliness point of view, which is important with seed, they are preferable. But they can be prone to leakage between the panels if they are not properly sealed when built.
“This store is sound, although there is a bit of leakage from one of the louvres.”
Mr Cunnington says repairing the leaky louvre should be a priority as warm air blowing into the store from outside would result in condensation on the crop which encourages disease.
The store is holding multiple stocks with an impressive wall chart ‘map’ showing where the numerous boxes of varieties are stored.
Mr Smith says: “We keep good records of where every seed box is.”
A mixture of refrigeration and ambient air circulation is used in the store.
Stores 1 and 2: Processing potatoes
Store 3: Short-term storage of prepack potatoes
Store 4: Seed potatoes
CIPC is a persistent chemical and store managers will need to follow cleaning guidelines to meet a new temporary maximum residue level.
Dr Mike Storey, chair of the Potato Industry CIPC Stewardship Group, says businesses which have not been monitoring technical messages will be at risk of crops not passing inspection.
“This will become an issue at the point at which the maximum residue level (MRL) of CIPC allowable on potatoes for human consumption, which is currently 10 parts per million, drops to a new temporary MRL [tMRL]. We think this will happen before the 2020 harvest comes out of store.
“We don’t yet know the tMRL rate, although AHDB has been part of a Europe-wide effort to submit data from commercial stores to inform this. We know where we hope it will be and it is at a level which will be achievable if you’re using stores that have previously used CIPC, as long as cleaning guidelines are followed – but if you apply CIPC to crop this year  it will not pass an inspection.”
Mr Cunnington believes many growers are familiar with the changes and will know that the 2019 harvest is the last which can be treated with CIPC.
He says: “Most growers are on top of this situation, but we are still receiving some worrying reports that there are producers who are not fully aware of the changes and their consequences.
“Any grower who applies CIPC in autumn 2020 is at a high risk of being unable to sell that crop. Our message is quite simple when it comes to CIPC at 2020 store loading. If you fog them, you can’t flog them.
“Our advice is to dry clean if there is nowhere to dispose of water safely. Removal of CIPC is important to ensure there is the lowest possible risk of contamination and to ensure crops do not exceed any tMRL,” adds Mr Cunnington.
Where there is a CIPC legacy, stores need to be hoovered thoroughly to get rid of the dust. Mr Smith says stores at JSR Farms are cleaned routinely every year and they can dispose of waste in a controlled way, which is essential where chemical is being removed.
With boxed potato stores where CIPC has been used, Mr Cunnington suggests putting boxes outside to air in summer. UV from the sun also helps break down any CIPC residues.
AHDB is offering free one-to-one potato store visits to levy payers via its new Storage Network. The visits are designed to help businesses prepare for life after CIPC but are also available to growers who do not use the chemical.
Store managers can sign-up for their visit via the AHDB storage hub or by calling 01406 359 419.