Postharvest disease management of horticultural produce using essential oils: today’s prospects (2010)

of review : This article provides a summary of the published research pertaining to the antifungal properties of some essential oils and their components that could be potentially used to control postharvest pathogens in fresh horticultural products. The mode of action, synergistic effects, phytotoxicity, legal and safety aspects are also discussed. Findings : In vitro studies have demonstrated the antifungal activity of essential oils against a range of postharvest pathogens including Botrytis cinerea , Penicillium spp., Alternaria spp., Aspergillus spp., Monilinia spp., Geotrichum candidum , Colletotrichum spp. and Fusarium spp . Although the inhibitory effects of essential oils on these fungal pathogens have been mostly attributed to a synergistic effect between the active ingredients, some individual components of the oils have also been identified as effective antifungal sub4 stances in vitro . These refer to carvacrol, anethole, thymol, decanol, cinnamaldehyde, eugenol, citral, terpinen444ol, α4terpineol, cuminaldehyde, perillaldehyde, salicylaldehyde and benzaldehyde. Essential oils have been shown to be more effective on postharvest pathogens in in vitro bioassays compared to in vivo applications. The two main issues encountered during the in vivo evaluation of the essential oils are phytotoxic effect and tainting of the organoleptic properties of the produce. The inhibitory effects of essential oils appear to be dependent on a number of variables such as target microorganism, host, concentration and method of applying the essen4 tial oils. Limitations : To be suitable for postharvest disease management, essential oils should retain their antifungal activity over a long period of time, meet safety requirements in terms of human health and environment, not diminish the quality of the produce, and be cost- effective for growers and producers. None of the essential oils tested for their antifungal properties to date have met all of these require4 ments. However, as the research and in particular, the practice of using essential oils for postharvest disease management on horticul4 tural crops is still in early development, it is currently difficult to provide an accurate statement on limitations when not all of the factors contributing to the in vitro and in vivo efficacy have been elucidated. Directions for future research : Essential oils appear to be a promising alternative that may subsequently lead to the development of novel postharvest biofungicides to be used on fresh horticultural produce. These could potentially reduce/replace the synthetic fungi4 cides that the global horticultural industry is highly reliant on at the present time. Given consumer and legislative concerns over the use of synthetic fungicides, essential oils should be able to capture reasonable market share given comparable efficacy and cost. While this potential exists, the factors influencing the in vitro and in vivo effectiveness of these plant volatiles need to be elucidated. Additionally, in order to meet industry and consumer's expectations, large4scale trials should take place under commercial and semi4commercial conditions for different horticultural commodities, which not only consider efficacy but also cost, legal, and safety issues.