Pg. 28-30 The effect of pre-harvest application of fungicides on post-harvest decay development on litchis

In South Africa there are currently no registered pre-harvest fungicides for the control of post-harvest decay of litchi fruits. The aim of this trial was to determine the effect of pre-harvest application of fungicides on post-harvest decay control. The trial was conducted in the Tzaneen area on cultivars Mauritius and McLean’s Red. Five fungicides, applied 14 or 21 days before harvest, were tested during the trial. Phytex 200 and Ortiva reduced post-harvest decay the best when sprayed 14 days before harvest on cultivar Mauritius. However, when sprayed 21 days before harvest, Topsin and Prochloraz reduced post-harvest decay the best. None of the fungicides sprayed on cultivar McLean’s Red effectively controlled post-harvest decay compared to the unsprayed control treatment.

Summary:

• Objective: The study investigated the effect of pre-harvest fungicide application on post-harvest decay development in litchi fruits, focusing on the cultivars Mauritius and McLeans Red in South Africa.
• Context: There are currently no registered pre-harvest fungicides for controlling post-harvest decay in litchis in South Africa. The research aimed to assess whether certain pre-harvest fungicide treatments could improve post-harvest decay control.
• Methodology:
  • Five fungicides were tested: Phytex 200, Ortiva, Topsin, Prochloraz, and Copper Count N.
  • Fungicides were applied either 14 or 21 days before harvest.
  • After harvest, fruits were evaluated for decay over a 40-day period simulating export conditions.
  • Some samples also received a post-harvest prochloraz dip, but these results were not included in the main efficacy assessment.
• Findings for Mauritius cultivar:
  • 14 days before harvest: Phytex 200 and Ortiva gave the best control of post-harvest decay.
    21 days before harvest: Topsin and Prochloraz were most effective.
  • All treatments reduced decay compared to the untreated control, which had a very high percentage of decayed fruits.
• Findings for McLeans Red cultivar:
  • None of the fungicides tested showed effective control over post-harvest decay compared to the untreated control, regardless of timing.
• Comparative Results:
  • Overall, fungicide treatments were more effective on Mauritius than McLeans Red.
  • Timing of application influenced efficacy: for Mauritius, Phytex and Ortiva worked best when applied closer to harvest, while Topsin was better when applied earlier.
• Additional Insights:
  • The efficacy of fungicide treatments can be further improved with post-harvest prochloraz treatment, but this was not analyzed in detail.
  • Effective post-harvest decay control should incorporate pre-harvest sprays, post-harvest fungicide dips, optimal packaging, and proper cooling during export.
• Recommendations:
  • Establish specific fungicide programmes for different litchi cultivars.
  • Further research is needed, especially with consistently effective agents like Phytex and with biological control options.
  • Strobilurine fungicides (such as Ortiva) should be further evaluated, especially for cultivars with weaker response.
• Conclusion: Pre-harvest fungicide application can reduce post-harvest decay by up to 53% in certain litchi cultivars. Treatment effectiveness is cultivar-dependent and influenced by timing, so tailored programmes and additional research are recommended.