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Storage Bulletin - October 2014

Publication Date: 
24 October 2014

AMBIENT AIR SHORTAGE HINDERS COOLING AND DISEASE CONTROL
 
Despite a week of relatively cool nights, September was one of the warmest and driest on record and early October has continued to be unseasonably mild. This has meant that, whilst harvest was able to start earlier than normal, there has been a shortage of cooling in many ambient stores.
 
This prolonged warm spell has started to have impact in some potato stores with an increasing and concerning number of enquiries coming in about breakdown, across a wide range of varieties.
 
Some of the samples which have found their way to SBCSR have been identified as suffering from watery wound rot (caused by Pythium ultimum, pictured below left) but not all the infections have been fungal; several have been purely bacterial soft rot, often associated with poor skin set. Tuber blight (caused by Phytophthora infestans, below right) has also been reported. 
 
For more information on potato diseases visit the AHDB Potatoes Pests & Diseases Tool.
 
Watery wound rot Tuber Blight

 

 
The continued mild weather during early October can only be increasing the disease pressure within those stores which do not have refrigeration and are unable to be adequately cooled. It is therefore crucial that store managers take specific action in their management as follows:
 
  • Inspect crops thoroughly and regularly for any signs of disease development or breakdown, such as dripping, smell, presence of fruit flies etc. Sprout control may also be compromised if there is rot present.
  • Use the maximum amount of air available to dry any affected stocks (set any inverters to 50Hz or maximum). Ensure the air is effectively applied to crop wherever possible by closing laterals, eliminating short circuits etc
  • Maximise the options for cooling by running stores on automatic control. If possible, with axial (propeller-like) fan systems, try to reduce the ambient/crop differential to around 1.5°C, if your controller permits this. This will increase the time when cooler air can be blown in the short term. Remember to restore the setting to c. 2°C for the winter months!
  • If bacterial rot is developing, try to get temperatures down below 10°C to  reduce the rate of bacterial multiplication. In these circumstances, re-assess the likely storage life and be prepared to move crops earlier than planned, especially if disease affects over 1% of tubers.
  • In the longer term, if slow autumn cooling is a recurring problem, to consider adding refrigeration to the store or making changes to the ventilation system to increase air volumes (giving more rapid response) or improve the effectiveness of air use (eg through the addition of an air separator curtain, pictured below, in an overhead throw box store for £2-£4/tonne).
Air separator curtain in a box store

 

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