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Storage Bulletin - August 2012

Publication Date: 
17 August 2012

A challenging year?

The new season for storage is fast approaching and, as store managers, there are several challenges potentially coming our way. Judging by some of the field reports, there is as strong a case as ever to be prepared so that crops can be brought under control quickly and give the best chance of maintaining quality tuber integrity and quality in store.

A key task for many growers will be crop segregation prior to harvest. Making the decision in the field as to what will store and what won’t is much better than having to deal with the problem after the crop has been loaded. If there is crop which has been waterlogged or seriously infected by blackleg and/or blight, this really needs to be kept separate to minimise its impact on the storage life of other parts of the crop which might be less badly affected. A separate short term storage area or boxes which can be put on to a drying wall might be used for anything which is looking dubious. Blackleg and foliar blight levels are reported to be at least on a par with 2007 and, in contrast to that year, tuber blight risk remains high whilst the field conditions remain warm and moist.

Hopefully the weather will be kind and we won’t have to deal with wet crop on top of all the potential problems that are already in the field but we need to be prepared. There are already signs that soils are drying out in some parts of the country which should aid storage potential but where field remain wet the disease risk will be high – especially if that combines with warm temperatures in the lead-up to harvest. Problems such as pink rot are associated with waterlogging and could be a threat. These fungi can potentially infect crops very quickly so there will be a need for increased vigilance to spot any signs of infection early.

In all cases, the availability of air will be crucial to drying and cooling crops when they come into store and this will be most effective if that air can be delivered positively. Bulk stores with lateral ducts and specially-designed box systems, such as letterbox or suction wall layouts, will perform best. In overhead-throw stores, it is crucial to ensure a circulation of air through the boxes and to block off any opportunity for short-circuiting. This will be particularly important if stores are not filled to capacity. Call 0800 02 82 111 if you need advice on box stacking.

In ambient stores, there can be a risk of condensation especially if the weather turns warm after loading. External air blown on to cooler potatoes will help to dry them as long as temperature differences are small (say below 3°C). At any larger differential there can be a risk of condensation. Watch for this in bulk stores too when recirculating warmer air from the roof space back into the base of the pile.

CIPC use

Prior to application of CIPC this season, there is a new requirement (which will be audited under Red Tractor Assurance) to assess the suitability of  stores which are subject to treatment before the first treatment is applied. A simple checklist has been devised which must be completed by the store owner for each store to be treated. The checklist is available at www.potato.org.uk/cipc.

Where CIPC sprout suppressant is being used, application can take place once crops are dried and cured. The speed of curing is most significantly influenced by temperature as shown below.

Wound healing rate in relation to crop temperature
Temp (°C)            Initial suberisation (days)         Periderm complete (days)
   < 5                                             7 – 14                                          21 – 42
   10                                                4                                                 7 – 14
   20                                             1 – 2                                              3 – 6

Unless temperatures are particularly cool, initial suberisation is achieved quite quickly and therefore the first dose of CIPC can be applied during the pull-down phase. This helps to ensure that control is not delayed and that the use of CIPC is optimised. Research has shown that early application can reduce the need for repeat doses and, with CIPC under continuing stewardship, it is important to make best use of every treatment.

Uniform distribution of any CIPC applied is essential for good sprout control. Inverters can help achieve this in bulk stores. In boxes, forming a plenum (closed duct) into which the CIPC can be applied is recommended. A best practice guide is available; download it from www.potato.org.uk/cipc or call 0800 02 82 111. It is important to stress that, if even distribution is not being achieved, additional doses of CIPC are unlikely to help until this has been resolved. Parts of the store where CIPC is not being adequately distributed will show the first signs of sprouting but adding more will not help if the CIPC is not reaching these areas. It will merely increase the risk of exceeding the MRL of 10 mg/kg on crop where CIPC is not deficient. This is a key point to bear in mind when considering a repeat application, especially in stores where the rate of CIPC decline is low – e.g. closed refrigerated stores.

Store management introduction

There’s still time to grab one of the last places on the Introduction to Store Management course being held at Sutton Bridge on 29 August. Go to www.potato.org.uk/events/introduction-potato-store-management for more details.

Event dates

Please see www.potato.org.uk/events  or call 0247 647 8782 for further information.

East of England Potato Day, Bury St Edmunds, Suffolk. 30th August

North of England Potato Day, Tadcaster, Yorks. 4th September

North West Potato Day, Runcorn, Cheshire. CHANGE OF DATE: 18th September

AHDB Potatoes Seed Industry Event 2012, Crieff. 20 November.

AHDB Potatoes Storage Day, Sutton Bridge CSR, Lincs. 29 November, 10am-4pm
A unique day for growers and agronomists to benefit from the latest research and advice where experts will discuss key storage challenges and provide guidance on how to get the best from your storage. Trade stands and sponsorship opportunities available. BASIS & NRoSO accredited. Evening reception with speaker on 28 November.

See www.potato.org.uk/events/sutton-bridge-storage-day for more.
 

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