| Summary: | Green and blue molds, caused by the fungi Penicillium digitatum and P. italicum, respectively, are the most economically important citrus postharvest diseases in Mediterranean climate areas such as Spain. Due to its high efficacy, persistence, and antisporulant activity, imazalil (IMZ), an imidazole, is the most used synthetic chemical fungicide to control these diseases worldwide. However, due to health and environmental issues, export markets and commercial channels are increasingly demanding citrus fruit with null or reduced fungicide residues. Furthermore, in the European Union, this is also an important requirement of the Farm to Fork strategy for agricultural production within the European Green Deal. Nevertheless, in terms of design of antifungal postharvest treatments, fungicide residue reduction needs to be correctly done to avoid the lack of treatment effectiveness and the proliferation of resistant strains of the target fungal pathogens. In this work, low IMZ doses (25 and 50 ppm) were combined with the food additive (E211) and generally recognized as safe (GRAS) compound sodium benzoate (SB) (3% w v-1) and heat in dip trials with citrus fruit artificially inoculated with P. digitatum or P. italicum. Dip treatments at 50ºC for 60 s with IMZ+SB resulted in reductions of the incidence of green and blue molds with respect to control fruit (treated with water at 20ºC) higher than 90% on ‘Valencia’ oranges incubated at 20ºC for 7 days, while IMZ or SB alone at 20 or 50ºC reduced disease incidence by 50-70%. Similar results were obtained when 25 ppm IMZ, 3% SB and the combination of these treatments, all applied at 50ºC for 60 s, were tested on artificially inoculated ‘Lanelate’ oranges and ‘Ortanique’ mandarins incubated at 20ºC for 7 days, and also on ‘Valencia’ oranges cold-stored for up to 8 weeks at 5ºC followed by a shelf-life period of 1 week at 20ºC. Therefore, heated mixed aqueous solutions of IMZ at low doses and SB may be an interesting integrated tool to reduce postharvest fungicide residues on citrus fruit while obtaining high decay control levels.
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