Potential use of thymol to control fruitlet core rot (FCR) in pineapple cultivar ‘Queen Victoria’ in Reunion Island

Fruitlet core rot (FCR) is one of the major postharvest diseases of pineapple (Ananas comosus var. comosus), especially on the prone cultivar 'Queen Victoria' cultivated in Reunion Island. This aggressive disease is generally due to two pathogens, Fusarium ananatum and Thalaromyces stolii and needs to be controlled during postharvest. In Reunion Island, F. ananatum is the principal causal agent impacting fruit exportation. Fruit produced for the export market are generally treated with chemicals. This type of postharvest treatment is not in line with consumer expectations, as consumers prefer fruits treated with nonharmful and natural products. The objective of this work was to study alternative postharvest treatments using the fungitoxic properties of essential oils. Six oils were tested in vitro on mycelial growth of F. ananatum. The thymol, a natural molecule synthesized by thyme (Thymus vulgaris L. thymoliferum) is the more effective in vitro. Thymol, prepared at 0.025% in a terpene solvent that acts as a penetrating agent, was tested in vivo with inoculated fruits. The treatment was effective only on young necrosis and did not have any negative effect on fruit quality. Results and opportunity of this treatment are discussed.