A new method for the postharvest application of imazalil fungicide to citrus fruit

Fungal infections contribute significantly to postharvest losses of citrus fruits. Imazalil (IMZ) is currently the most commonly used fungicide that is effective for controlling postharvest fungal pathogens in citrus. IMZ is currently used in Italy as a wax emulsion for application by spraying. This system simplifies treatment, but it requires high IMZ concentrations to be effective, which result in large amounts of fungicide per unit mass of citrus fruit being applied. This paper describes tests with a pilot plant utilised to develop a method called Imazalil thin film treatment (ITFT). The method is designed to reduce the amount of fungicide used and problems related to wastewater disposal. The efficacy of three methods of fungicide application were tested, spraying, dipping and ITFT. The decay of fruit and IMZ residues in fruits were evaluated over a 60-days storage period at 5°C and after one week of shelf-life at 20°C. At the end of the shelf-life period, the incidence of cumulative fruit decay after ITFT treatment (10.4%) which did not significantly differ from that of spraying (11.5%), but it was significantly higher than that of dipping (3.0%). During storage, the level of IMZ decreased for all treatments following first-order destruction rate kinetics (with a half-life of 19.4 d). For the dipping and ITFT treatments, IMZ residues were significantly higher than the residues in the spraying treatment. Further, significant differences in the IMZ residues were found between the dipping and ITFT treatments.