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Post-harvest treatment of apples


This section of the Guide has changed significantly since the first edition was produced in 2001. At that time, a number of fungicides were registered for use on apples as a post-harvest dip or drench.

There are currently no fungicides registered in the UK for post-harvest application to apples.

Several factors have contributed to this situation. The main factor has been public concern over the use of pesticides and chemical residues in food at the time of consumption. Clearly the general public does not appreciate the concept of MRLs  and wants no detectable pesticide on the food when it is eaten.

A second important factor has been the realisation that the application of fungicides to apples after harvest has only a limited effect in reducing fungal spoilage. More effective control of rots can be achieved by chemical intervention in the orchard to prevent initial infections and much can be done with a non-chemical approach. Other factors of concern about post-harvest fungicide use include the problems associated with disposal of drench solutions.

Information on the post-harvest application of fungicides is no longer relevant since there are no products approved for this use in the UK.

In addition to fungicide dips and drenches, this section of the guide provided guidance on the post-harvest applications of calcium products to apples in a similar dip or drench method. However, this too is no longer practiced in the industry and no calcium products appear to have recommendations for this type of application any longer.

There is an increasing use of biological agents to control disease and in future, it is possible that these may be used as post-harvest application. The information below has therefore been retained in this section should further approvals be released for any form of post-harvest application.


Equipment calibration for post harvest treatment

The following procedures should be adopted for calibration:

  • Measure volume of tank.
  • For square tanks calculate volume = height x length x width.
  • For round tanks calculate volume = radius x radius x height x 3.142.
  • For measurements in metres multiply volume (cubic metres) by 1000 to provide volume in litres.
  • For measurements in feet multiply volume (cubic feet) by 6.24 to provide volume in gallons.
  • Measuring jugs and scales should be specific for the job and not used for any other purpose.


Good practice preparing for post harvest treatment

The following procedures should be adopted for operation:

  • Mark the tank to show the operating level (full).
  • Add clean water until the tank is approximately three-quarters full.
  • Use a clear area to weigh or dispense chemicals.
  • List chemicals and quantities used in each tank mix.
  • Dilute the concentrate in the ratio of 1 part chemical to 9 parts water. Always cream wettable powders in water before adding to the tank.
  • Add to the tank and fill to the mark. Mix for at least 10 minutes.
  • Label tank clearly with contents.
  • In order to prolong the life of the solution any soil should be removed from the outside of bins to prevent soiling of the yard and of the drenching/dipping solution.
  • Separate the bin reception area from the standing area for treated bins.


Good practice during post harvest treatment

  • Treat fruit for 60 seconds maximum.
  • Fruit should not be treated above 210C or below 100C (optimum 160C).
  • Top-up using solution diluted to the correct concentration.
  • Change solution every 2 or 3 days or when excessively dirty. DPA manufacturers suggest refilling with fresh solution after every 100 bins.  This may be fewer than are treated in practice, particularly where dip tanks are used.


Good practice following post harvest treatment

  • Dispose of the used (dilute) solution  on an area of land authorised for the purpose by the Environment Agency, via a licensed waste disposal company or by the use of equipment designed specifically to treat waste pesticides.
  • After chemical treatment allow the fruit to drain  before stacking into a store that has been cooled thoroughly prior to loading.
  • Stores with insulated floors should be pre-cooled for 5 days and those with un-insulated floors for 10 days.
  • Ensure that the refrigeration plant is switched off during loading. Use other available stores for pre-cooling fruit prior to loading.
  • Ensure that fruit reaches the final holding temperature within 5 days of the start of loading.