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Storage Bulletin - November 2016

Publication Date: 
24 November 2016

Winter Watchout 

Disease & condensation

Following a relatively dry and warm harvest, most crops are reported to have gone into store pretty well. But there is no room for complacency, especially with a few problems being consistently reported to be around like late blight (Phytophthora infestans) and blackleg (Pectobacterium). 

Depending on the severity of the problem and conditions in store, these diseases have potential to continue to develop, so it is important to watch out for any signs of breakdown such as smell or ‘leaking’ under boxes or in lateral ducts. If there are any suspicions, take samples from around the store and wash/inspect them to quantify the risk. Use the AHDB Pest & Diseases Tool to help identify any problems.

A crucial factor in disease development is the presence of moisture and, as ambient temperatures start to fall, particularly at night, the risk of structural condensation within stores increases. This can be a problem if it starts to drip onto and wet potatoes.

The crop gives up moisture to the store environment by evaporation through the skin and from respiration so the storage environment typically equilibrates at a relative humidity in excess of 90%.

Depending on the level of insulation in a store, it usually only needs a relatively small change in ambient temperature to result in condensation on the structure. Typically, within the normal temperature range used in processing stores, a 1 - 1½°C change in temperature will result in condensation. The cold surfaces of steel, for example, on the portal frame or roof purlins are often prone to showing the first signs of moisture.

The use of roof space heating can lower the risk of condensation as the electrical heater reduces the humidity of the store air. The heat should be thermostatically controlled to switch on if the air temperature in the roof space drops more than about ¾-1°C below the crop. Using perforated polythene ducting with a roof space heater is a good way of distributing the warm air evenly around the roof space. If no heating is available, use targeted recirculative ventilation to move air around and so reduce the risk of condensation.

CIPC re-treatment

CIPC remains under industry stewardship and its code of best practice requires careful and justifiable use of the chemical at all times. Accordingly, don’t make repeat applications to processing crops this winter unless there is a clear and demonstrable need for re treatment. The limit for 2016/17 is 42 grams CIPC/tonne on crops destined for processing and there is a 14 day withholding period after final treatment before sale. Data from continued research by Sutton Bridge CSR has shown that, in many cases where re-treatment takes place, it is often made too early or can even be, in some cases, unnecessary. If an initial dose has been correctly and evenly applied, CIPC will be uniformly available and will offer control at levels as low as 2 ppm throughout the store. As always, consult a BASIS advisor before making any CIPC application.

Remember, second applications of CIPC can no longer be made to fresh crops being held in cold stores at 5°C or below, but there are options to combine treatments with subsequent use of ethylene or spearmint oil. See our October storage bulletin for more information on these options.

Further guidance on CIPC use is available from the Potato Industry Stewardship website at

Forthcoming events

AHDB Agronomists' Conference 2016, Peterborough. 7 & 8 December 2016
A combined cross-sector event with a potatoes-focused programme on 7 December; cereals on 8 Dec. Peterborough Arena, East of England Showground, PE2 6XE

SPot Farms Results Days, January 2017: A summary of trials findings from each site.

SPot Farm West, 5 January at Kegworth Hotel & Conference Centre, Packington Hill, Kegworth, Leics. DE74 2DF

SPot Farm East, 11 January at Thetford, Norfolk. Venue to be confirmed.

SBCSR BASIS (Stored Potatoes) Course, 12 January 2017. Exam: 27 January 2017
A one day course with a formal exam a couple of weeks later. Limited places. Call 01406 359419 for booking information.

AHDB Potatoes Welsh Potato Day, Pembrokeshire. 19 January 2017
At The Pavilion, Gate 3, County Showground, Withybush, Haverfordwest, SA62 4BW  

SBCSR Store Managers’ Course, Lutterworth, Leics. 1 & 2 February 2017
Date and location now confirmed; full booking information available by calling 01406 359419 or email

AHDB South West Storage Day, Ilminster, Somerset. 1 March 2017
Diary date. Details for the day to follow.

AHDB Storage Forum, Red House Hotel, Coupar Angus, PH13 9AL. 9 March 2017
Another diary date. A programme for the day will be confirmed shortly.

SBCSR Storage Showcase, 8 June 2017
A knowledge exchange day on storage, to be held at Sutton Bridge. Please save the date; further information will follow early in the New Year. Exhibitor space will be available.

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