The control of postharvest blue and green molds of citrus in relation with essential oil–wax formulations, adherence and viscosity

The use of wax coatings enriched with antifungals has significantly contributed to quality maintaining of harvested citrus fruit. On the other hand, interest in essential oils (EOs) as an alternative to synthetic fungicides has recently gained momentum. In this study, Cinnamomum zeylanicum EO was incorporated into a variety of commercial citrus waxes (shellac, carnauba, paraffin and polyethylene). The biological activity of these formulations against green and blue rots as well as their viscosity and adherence to the orange fruit surface were evaluated. Excellent disease control was achieved with C. zeylanicum EO incorporated in shellac and/or carnauba wax compared to other EO–wax formulations. Disease control by EO–waxes seems to depend not only on the volume that remains on the fruit skin, but also, probably on the retention of EO components on the fruit. Other factors such as formulation solubility, permeability to gases, and compatibility between EO compounds and those of waxes may also be involved in the improvement of EO efficacy. The present study may therefore allow a careful selection of appropriate waxes for the elaboration of effective EO–wax formulations.