Plenty to discuss at EAPR post-harvest potato meeting

Potato researchers, agronomists and others from across the world met in Norwich in March for the 2019 biennial Post Harvest Section Meeting of the European Association for Potato Research (EAPR). With the industry expecting to lose access to sprout suppressant chlopropham (CIPC), new restrictions on the use of maleic hydrazide (MH), and renewed attention on acrylamide in processed potato products, there was plenty to discuss.

After a series of presentations from agri-tech companies, arranged by Agri-Tech East and AHDB Potatoes, organisers Glyn Harper of AHDB Sutton Bridge and Tjaart Hoffman of Certis Europe welcomed delegates to the event, while Mark Taylor, chair of the Fresh Potato Suppliers Association (FPSA), set out what the whole potato industry would like to see from the research agenda over the next few years. Pointing out that more than 60 per cent of the UK crop is stored for a period, he urged everyone in the supply chain to “address challenges for the here and now.”

As well as tackling waste, improving productivity and building market share, Mark pointed out that, “we have some real challenges in the UK around storage and particularly sprout suppressants and they are giving us real cause for concern. I think that we have lost CIPC now in the UK and it is only a matter of time until it [is unavailable]… At the moment we are talking about an increasing list of things that we are not going to be allowed to use in the future. Our opportunities and our list of actives are getting less.”

MH stock feed restrictions

New requirements preventing the use of potatoes treated with MH for stock feed means that different packers, processors and supply chains will have to make their own individual decisions on whether or not they can segregate treated and non-treated potatoes, and whether or not MH can be used on crops supplied to them. However, Alain Berthet of chemical producer Kreglinger, and Bert Callebaut of Certis Europe stressed that without the availability of CIPC, MH would become ‘an indispensible tool’ for the control of potato sprout control, particularly in countries like the UK where other sprout control products are currently not available.

Alain Berthet stressed that the ‘specific provision’ under EU regulation 2017/1506 which related to the uncertainty over the effects of the metabolite 3-pyridazinone on livestock, did not amount to a blanket restriction on feeding. He said it put the emphasis on national member states to consider the issue, adding that the Belgian authorities believed that such a requirement could even be a drafting mistake.

However, the two different manufacturers of distributors of MH for crop protection in the EU had taken different approaches and while Kreglinger and DREXEL sought further information, Arysta had taken the proactive decision to introduce a label restriction on feeding treated potatoes to livestock, something which had also been adopted by CRD in the UK.

In the meantime, the industry is busy working to produce the necessary scientific information on the environmental fate and livestock toxicity of 3-pyridazinone, in the hope that the chemical will prove benign and the restrictions on MH can be removed. Otherwise Alain warned the restrictions could have the unforeseen consequence of creating up to one million tonnes of additional waste from UK potato processing which would have to be disposed of via landfill, and such unforeseen issues were also picked up by AHDB’s Mike Storey in his presentation on product stewardship.

“Are there lessons from the stewardship of CIPC for products such as maleic hydrazide?” he asked. Stressing that MH is required by the industry as part of an integrated sprout control strategy, he explained; “there have been restrictions imposed on the new label. Going forward you will not be able to feed MH-treated potatoes to livestock and that has very significant implications to the industry. Alongside that restriction there is a requirement from CRD for approval holders to put in place a stewardship programme to ensure there is compliance with this label restriction.”

In effect the industry currently has three options, which will narrow to two once existing stocks of ‘old label’ MH products have been used up by 30th April 2020. The first is for processors and packers to only accept potatoes treated with ‘old label’ MH products (not an option beyond this season); the second is to accept MH treated potatoes and ensure that either they are adequately segregated from un-treated, or that nothing from the supply chain is fed to livestock; while the third is to not accept MH treatment and continue to send all waste potato streams to stock feed.

“The unintended consequences of the label decision are that you won’t be able to get the benefits of MH for volunteer control and all that provides in terms of PCN, blight and virus management,” said Mike Storey.

Alternative sprout control products

It is a source of frustration to many UK potato growers and agronomists that many of the alternative sprout control products which are available to growers in other countries are not approved in the UK. A number of these were discussed in a series of presentations on the second day, including spearmint oil (Biox-M) which is approved in the UK; 1,4-Dimethylnapthalene (1,4DMN) which is now approved in 12 other countries around the world; and 3-decen-2-one (SmartBlock).

Kurt Demeulemeester of Inagro described trials which looked at all of these products, as well as CIPC (Gro-Stop Electro), ethylene (Restrain), and orange oil (Bio-024) on a range of processing and fresh market varieties including Markies, Innovator, Charlotte and Nicola. While CIPC performed well across all varieties, the best prevention of sprouting after 8 months was seen from SmartBlock, followed by 1,4DMN while Biox M provided control on a par with CIPC.

Potatoes treated with Bio 024 and Restrain had the longest sprouts after this period (up to 5mm in length), and both treatments also displayed the biggest variation in performance across different varieties.

With fewer sprout suppressants available, growers and store managers will need to take the natural dormancy of different varieties into consideration stressed Adrian Briddon of AHDB’s Sutton Bridge Crop Storage Research, who has been looking at dormancy since 2009.

“We do not have 1,4DMN, which is a source of frustration for our levy payers,” he pointed out, adding that processing growers in the UK have relatively little experience of using ethylene and spearmint oil. “If we have incomplete sprout control, such as not using CIPC, the impact of variety is much bigger,” he explained.

“If we look at more demanding long-term storage, such as nine months at nine deg. C, which is about as tough as it gets, we still have the pattern where short-dormant varieties are struggling and the longer dormancy varieties are succeeding. The dormancy of varieties is an important factor in the success of sprout control, but it isn’t the only factor.”

Effective store design

Store design and efficient airflow is known to also be an important aspect of being able to keep potatoes in optimum condition during storage and AHDB’s Adrian Cunnington gave an overview of work carried out on effective store design. Guy Willets of Assimilate Systems added to this by discussing the practical example of changes made at Winters Lane Store in Lincolnshire which used the common overhead-throw design.

“Just the one thing of rotating the refrigeration unit 180 degrees increased the overall volume of air moving through the system; front to back, left to right and top to bottom,” he explained. “That 15 per cent increase in the amount of air that we got through the system also led to a five per cent increase at the back end of the store. For such a simple thing to do, either in an existing store or when putting a new store in, it really adds value.”

Another commonly used technique to control sprouting is to lower the storage temperature, particularly in stores used for packing crops where low temperature sweetening and fry colours are less of an issue in the final product. However, Pia Heltoft of the Norwegian Institute of Bioeconomy Research warned that this would increase acrylamide levels in cooked products.

Acrylamide levels

Nigel Halford of Rothamsted Research stressed that this is becoming an even more important issue for the industry. Under European Commission regulation 2017/2158, which came into effect April last year, all food businesses have a responsibility to ‘monitor the levels of acrylamide in their products and to keep records of the mitigation measures they apply.’ In addition, if the recorded levels are not below the new Benchmark Level, these mitigation measures must be reviewed.

“If the new European Benchmark Level is confirmed at 750 parts-per-billion, we expect more than 10 per cent of samples to exceed it in the months from January to June,” he stressed. “You can see the importance of storage and there is a variety-dependent effect of storage as well. Potatoes should not be used outside their optimum storage window.”

He also questioned whether storing crops below 8 deg. C. is compatible with these new EU requirements on acrylamide. “I think retailers store at 4 deg. C and I think that is unacceptable,” Nigel added. “It is not clear whether the regulation that stipulates that product should be stored above 6 deg. C, which I would argue is already too cold, applies to the fresh fare market.”

As if the industry doesn’t have enough problems trying to keep crops cool enough to prevent sprouting but warm enough to prevent sweetening and potential acrylamide issues, the loss of approval of CIPC will create other pressing issues in terms of residues and crop availability.

CIPC decontamination

“The loss of CIPC will be worth around 12 weeks of crop self-sufficiency for the UK, resulting in a 50 per cent increase in supply costs,” warned Rob Clayton of AHDB Potatoes. However, more concerning may be the legacy issues of CIPC contamination from stores and boxes which have previously been exposed to the chemical.

With no product approval, the maximum residue limit for CIPC would normally fall to the limit of quantification (LOQ), but the contamination of building fabric, concrete and boxes is well documented, meaning that the industry is urgently pressing for the establishment of a temporary MRL which accounts for this.

“As AHDB, it is about supporting the approval holders to get things right,” explained Rob. “We are interested in supporting the routine monitoring that we will need to do across the fresh and processing associations, so we have our heads up and we know where the spikes are going to occur.”

With the wholesale replacement of stores uneconomic, there could be a demand for decontamination techniques which could be applied to existing stores, but here Rob sounded a note of caution: “Decontamination is an area we want to park for now until we get the temporary MRL sorted out. We have a particular worry that CIPC can now be detected in watercourses and we don’t want a panic within the grower base where everything is steam cleaned and we end up spiking the CIPC level in our watercourses.”

With so many challenges to address, the next few years will be extremely challenging for anyone looking to store potatoes in the UK for more than a couple of months.

As Rob Clayton concluded, “Our mitigations are a first-response and there are numerous fundamental research challenges still to address. Out fate is likely to be determined by the speed at which alternatives (to CIPC) are approved in the UK.”