PSI Bulletin: March 2025
Updated: May 26, 2025
No. 03/25 SUBSCRIBER EDITION: please go to potatostorageinsight.com/subscribe to sign up as a Synopsis subscriber.
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Dear Subscriber,
Welcome to the March edition of Synopsis.
Things are progressing fast at this time of year not least in the unloading of many potato stores, with a few problems coming to light as a result of poor harvesting conditions at the end of 2024.
See our section on Best Practice for more.
Out in the field, there are the first reports of growers planting across much of the country although continued cold weather at night has had many waiting in the starting blocks for a few more days...
PSI activity
Potato Store Managers' Course 2025
Our fourth annual Store Managers' Course of the post-AHDB era took place on 4th & 5th March at Greetham Valley in Rutland.
The course was very well supported with 25 delegates from as far afield as Cornwall, Scotland, Northern Ireland and the Netherlands coming together to discuss all things storage.
The interactive nature of the course was popular and culminated in some excellent presentations to address the scenarios put to each of the five groups in the final session.
There are no plans to repeat the residential course in 2025; the next one will be in early 2026. However, it is increasingly likely that one day modular courses will take place before harvest for seed/fresh and processing. PSI is currently accepting expressions of interest for both courses: please email adrian@potatostorageinsight.com if you are interested and have yet to get in touch.
Potato Storage Day
Plans are coming together to bring you another practical, grower-focused Potato Storage Day on Wednesday 21st May. PLEASE SAVE THE DATE IN YOUR DIARIES!
We have in excess of 15 organisations committed to involvement, so there will be plenty to see and hear about, all focused around storage.
Our venue is at Fleet Lodge Farm at Holbeach in south Lincs. It will be a free-to-attend half day event from 9.30am to early afternoon, with a light lunch provided courtesy of our main sponsors Farm Electronics and UPL.
The details of the event programme are still being finalised but, if you are interested in being a partner, having a stand or getting involved in the day's technical programme, please drop Adrian or Simon an email or give them a call: Adrian Cunnington 07970 072260 adrian@potatostorageinsight.com
Simon Faulkner 07850 649719 simon@sdf-agriculture.co.uk
Thank you to those who have already offered support; it is very much appreciated.
Please remember to register by emailing admin@potatostorageinsight.com in advance so we know how many people to cater for.
Best practice
Disease issues in storage
The last month has seen a number of diseases come to light in storage, some at serious levels. Here is a run down on some of the problems we are aware of:
ROTS
Bacterial soft rot (Pectobacterium spp.)
Waterlogging around harvest or crops which were simply loaded into store in wet condition and not adequately dried have been breaking down resulting in drips from laterals and boxes. This release of exudate quickly contaminates adjacent tubers resulting in breakdown of significant quantities of tubers over time especially if stores have been held at warm temperatures to maintain processing quality.
Any crops with in excess of 1% soft rot need to be unloaded quickly. If badly affected loads can be washed on farm before despatch, this will clean up contaminated stocks but usually won't prevent further degradation on delivery.
Dry rot (Fusarium spp.)
Characteristic fluffy mycelial growth and sunken wrinkled lesions on tubers are seen where dry rot has taken hold. It needs an entry point to infect - this is usually some form of mechanical damage - and is encouraged by warm conditions around harvest and early storage.
Over time, this breaks down through the invasion of the fungal rot by secondary bacteria resulting in soft rotting.
Gangrene (Phoma spp.)
Gangrene is another rot which infects through mechanical damage but, unlike dry rot, is encouraged by cool harvest conditions and inadequate curing. Late harvesting in cold, wet seasons usually results in a spike of gangrene infection which becomes most apparent at this time of year. Because it is associated with cool storage, it often develops slowly in store but, if invaded by secondary bacteria, can break down into soft rot.
BLEMISHES
Skin spot
Perhaps not surprisingly given the late end to last year's harvest, after such a wet October, this disease has been reported as a problem in storage this spring in susceptible varieties such as Sagitta, King Edward and Tyson.
Skin spot is a latent infection that often comes from infected seed, but is seldom identified when an affected crop is loaded into store. Spring inspections and wash-ups will show it if present and should prompt early unloading as the lesions can deepen over time, increasing peeling losses.
Technical insight
Reconditioning
There are reports of widespread variation in fry colour at the moment, probably stemming largely from the wide range of harvesting conditions crops were subjected to last autumn. One way to try to address a colour deficiency is to use reconditioning, a technique that can - if managed carefully - help to recover fry quality in processing potatoes. It is, at it simplest, a process by which the crop is warmed prior to unloading for 2 – 6 weeks to ‘burn off’ sugars to improve fry colour.
This graph helps to illustrate the pros and cons of reconditioning. It is from some trials undertaken at Sutton Bridge in the 1990s.
The dark line shows the control samples held at 5°C throughout the 9 month trial. For the most part the cool storage gives the poorest fry colours of all irrespective of storage term.
After 6 weeks of storage a set of reconditioning regimes were implemented, taking storage temperature up to 10, 15 or even 20°C for periods of 2, 4 or 6 weeks. At each stage, fry tests were repeated and a positive response of time and temperature can be seen against the Agtron (fry colour) scale.
This cycle of reconditioning was applied again after 18 weeks' storage and a smaller but still positive response in fry colour improvement was obtained.
The final reconditioning regime was applied after 30 weeks' storage, but it is evident that there is little or no response at this time. In fact, the only hint of improvement is in the 10°C reconditioning regime.
These data not only illustrate the upside of the reconditioning technique but also show that, in a variety prone to senescent sweetening like Pentland Dell, the crop passes a point of 'no return' where the reversible low temperature sweetening is overridden by senescence or 'old age' breakdown of starch into sugars. This response late in the season varied hugely by variety.
Senescent sweetening remains a threat to long-term stored crops in seasons when the crop is physiologically advanced.
Generally, there has been a move away from the more extreme elements of the reconditioning technique in recent years, but there remain advantages to be gained from gradual warming of stocks ahead of unloading to recover fry quality lost over a cold winter or due to variable growing or storage conditions.
CIPC data call: a reminder
Just One Test is all the CIPC Residue Monitoring Group needs from each potato store previously treated at any time with CIPC. If you have such stores, where crops are held for at least two months in the 2024/25 season, please provide data from your regular multi-residue testing to allow this to be used as part of the CRMG submission to be submitted in August 2025. We require 125 samples for the next data call, so new contributors are always welcome.
If you can help, please contact adrian@potatostorageinsight.com and you will be sent a simple data form (or download it via the link) to return with a copy of your lab result sheet. It’s as simple as that - but a vital role potato store managers can play to assist our industry.
Further information is available on the CRMG webpage at:
European developments
Meanwhile, changes are afoot in Europe with the authorities going through the process of lowering the temporary Maximum Residue Level (tMRL) for chlorpropham (CIPC) in the EU from 0.35 mg/kg to 0.20 mg/kg in time for the 2025/26 storage season.
No changes are anticipated in the UK.
Snippets
Infra-red thermal surveys
We are heading into a good time of year to do thermal surveys on potato stores. Why? Well, three reasons readily spring to mind: 1) with ambient temperatures now picking up it is an opportunity to get a good temperature difference across the structure which helps to accentuate any measurements 2) stores are staring to be emptied so that gives the maximum amount of time to undertake any remedial work before next harvest and 3} with more space available around the store comes the chance to get better access for making the measurements themselves.
If you're interested in having a survey undertaken, contact Adrian at PSI on 07970 072260 or email adrian@potatostorageinsight.com
Forthcoming events
If you are hosting a potato or agricultural industry event, please send details to admin@potatostorageinsight.com. Key dates with relevance to the potato sector in the coming months in the UK include:
May
Wed 21 Potato Storage Day organised by SDF Agriculture and Potato Storage Insight at Holbeach and sponsored by Farm Electronics and UPL.
Save the date! See further information above. More details to follow soon.
Fri 30 International Day of the Potato
June
Wed 11- Fri 13 EuroPatat Congress, Lille, France
Tue 17 CUPGRA field day, Cambridge
August
Thu 7 Potatoes in Practice. James Hutton Institute, Dundee.
November
Wed 19 - Thu 20 BP2025 - the British Potato Event, Yorkshire Event Centre, Harrogate
Exhibition, seminars and industry awards dinner. Save the date!
Details from: bpinfo@warnersgroup.co.uk
Please note that you, or a colleague, can subscribe to Synopsis at any time by going to potatostorageinsight.com and clicking on SUBSCRIBE. We can also now take payments by credit card. Call Adrian on +44 (0)7970 072260 if you have any questions.
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Synopsis is written by Adrian Cunnington and published by Potato Storage Insight Ltd., 45 Main St., Gedney Dyke, Spalding, PE12 0AJ. UK.
© Potato Storage Insight Ltd. 2025
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