- SH Swart
- QMS Agri Science, PO Box 416, Letsitele 0885, South Africa
- 2009
The effect of different hydrochloric acid (HCI) concentrations and exposure times, before, after or mixed with prochloraz or fludioxonil fungicides, with or without coating with Semperfresh, on weight loss, post-harvest decay and colour of litchi fruit was evaluated. Results showed that dipping fruit in 3% HCI for 120 sec, before or after dip treatments in prochloraz or fludioxonil, gave better control of post-harvest decay and prevention of pericarp browning than dipping fruit in 2% HCI for 300 sec. Acidifying of prochloraz or fludioxonil with 2% HCI improved decay control, but was detrimental to colour retention. Semperfresh, used in combination with HCI and fungicide dip treatments improved post-harvest decay control, but alternative products with better reduction of dehydration must be found.
Summary:
The study evaluated the effects of hydrochloric acid (HCl) dip treatments at different concentrations and durations, applied before, after, or mixed with prochloraz or fludioxonil fungicides, with or without Semperfresh coating, on litchi fruit weight loss, decay, and color.
Litchi fruit dipped in 3% HCl for 120 seconds before or after fungicide treatments provided better post-harvest decay control and pericarp browning prevention than dipping in 2% HCl for 300 seconds.
Acidifying prochloraz or fludioxonil with 2% HCl improved decay control but negatively affected fruit color retention.
Application of Semperfresh coating in combination with fungicide and acid treatments improved decay control but did not significantly reduce weight loss; better dehydration control products are needed.
Post-harvest decay commonly involves Penicillium spp., Alternaria spp., Botryodiplodia sp., Cladosporium sp., and Rhizopus sp.
Standard sulphur dioxide treatments effectively control decay but have drawbacks such as residue and poor color retention.
Fruit were evaluated after storage at 3°C for 40 days followed by 10 days at 10°C, simulating export conditions.
Weight loss was generally around 8.5% for control fruit and not significantly affected by the treatments.
Fungicide application timing (before or after acid dip) influenced decay control and color, with prochloraz applied before acid dip showing better results.
Both prochloraz and fludioxonil fungicides significantly improved decay control compared to no fungicide when combined with acid dips.
The addition of Sporekill (a sanitizer) did not improve decay control or color retention.
The best overall post-harvest decay control and color retention achieved with dipping in 3% HCl for 120 sec, followed by 405 ppm prochloraz or 300 ppm fludioxonil, and Semperfresh coating.
Future research suggested on acidifying fungicide mixtures with shorter exposure times and use of higher acid concentrations to improve color retention and reduce treatment steps in the packhouse.
Results support alternatives to sulphur dioxide fumigation for local market litchi with effective decay control and reasonable color preservation.