Survey and investigation on the impact of various fungicide application methods and technologies on decay control of plums in the pack-house

Application of fungicides may be highly efficient for control of post-harvest decay of plums. However, successful control, without exceeding maximum residue limits, relies on appropriate and optimized fungicide application, dosages and methods. The aim of this study was to conduct a survey at various packing lines in plum pack-houses in the Western Cape to determine and review the specifications at which fungicide application technologies are used.

In the first year, atomiser systems of seventeen plum packing lines were surveyed to determine which fungicide application technologies were prevalent, and to gather information on system specifics. In the second year, selected packing lines were re-surveyed to establish if improvements had been made as a consequence of the first year’s findings and recommendations

• It was established that three fungicide atomising systems were in use:
  1. Atomisation by nozzles driven by compressed air (60% of packing lines)
  2. Atomisation by nozzles driven compressed (hydraulic) fluid (10% of packing lines).
  3. Atomisation by spinning disks (30% of packing lines)

• Factors critical for successful fungicide application using the atomizers were identified as:
  1. Condition of the pumps
  2. Mixing of the fungicide product
  3. Condition of the pipes transporting the fungicide product
  4. Concentration of the fungicide product
  5. Spray deposition of the fungicide product on the fruit ( number of heads, spacing, etc)

Fungicide cost cannot be considered a major driver in decisions regarding fungicide application, when application methods do not deliver the product effectively. Despite the certain problems identified, it was pleasing to establish that all the atomiser systems surveyed were capable of delivering adequate coverage of fungicide product to fruit. Focussed management of the critical factors influencing atomiser efficacy, as identified in first year of the study, was shown to improve fungicide spray deposition as evidenced in the second year.

Good information to assist pack-house users optimize atomisers for post-harvest fungicide application is provided in the report, with graphic illustrations to assist. In addition, a guide to assist optimization of atomiser systems on plum packing lines is summarized in the Conclusions Section of the report.