Prevalence of Postharvest Diseases of Mandarin Fruit in California

Abstract

In recent years, storing mandarin fruit in cold facilities has become a common practice to retain fruit quality and expand the marketing window, but postharvest diseases can limit the storage period for the fruit. To identify major postharvest diseases affecting mandarins, decayed fruit were collected from 20 and 46 grower lots in 2015 and 2016, respectively, either at presorting or after cold storage. Fungal isolation and identification were attempted for all decayed fruit. Alternaria rot caused by Alternaria spp. was most prevalent on nonstored fruit collected at presorting, accounting for 53.5% and 83.1% in 2015 and 2016, respectively. On stored fruit collected after cold storage, green mold caused by Penicillium digitatum (36.3%) was most prevalent followed by Mucor rot caused by Mucor piriformis (27.7%) and blue mold caused by P. italicum (23.3%) in 2015, while gray mold caused by Botrytis cinerea (29.7%) was most prevalent followed by Mucor rot (27.1%) and sour rot caused by Geotrichum citri-aurantii (18.7%) in 2016. Our results indicate that gray mold and Mucor rot are two emerging postharvest diseases of mandarin fruit in California and that postharvest disease-control programs for mandarin fruit should target not only common postharvest diseases such as green mold, blue mold, and sour rot, but also emerging diseases Mucor rot and gray mold.