Effect of gum arabic enriched thymol and salicylic acid composite coatings on B. cinerea and M. laxa in harvested plums (‘Angelino’)

Stone fruit pathogens Monilinia laxa and Botrytis cinerea, causing brown rot and grey mould, respectively, result in major postharvest losses of plums worldwide. The alternative bioactive thymol and salicylic acid are potential antifungal compounds for brown rot and grey mould control of stone fruit. This study aimed to verify the efficacy of salicylic acid and thymol in vitro and fruit inoculation trials on the plum cultivar ‘Angelino’ treated curatively with edible coating. The fruit was stored at shelf life conditions of 25°C and evaluated for decay severity after 4, 6, 8 and 10 days. Media amended with thymol at concentrations ranging from 0.005 to 2.5 mM effectively inhibited the growth of both pathogens at 0.25 mM (M. laxa) or 1 mM (B. cinerea). The tested salicylic acid concentrations ranging from 0.005 to 4.7 mM did not show complete fungal inhibition in in vitro tests. Both applications of salicylic acid (2 mM) and thymol (4 mM) reduced decay by more than 50% during the 10-day shelf life storage for both pathogens.