Dry lenticel rot – an emerging postharvest disease on apples in northern Italy: insights from inoculation assays

Ramularia mali is an emerging postharvest pathogen of apples, causing dry lenticel rot symptoms during extended cold storage. Since its first observation in 2012 in Piedmont and South Tyrol, Italy, cases have increased significantly, with recent reports from Austria and France. Despite the asymptomatic nature of R. mali infections in the field, symptoms manifest only after prolonged storage. This study investigated the pathogen’s behavior through inoculation assays using three methods: injection, puncture wounds, and immersion, followed by storage for up to 7 months. Two isolates, one from symptomatic fruits of ‘Golden Delicious’ and the R. mali type culture (CBS:129581), were used for inoculation at harvest and postharvest intervals. Injection of conidial suspension caused symptoms in 100% of fruits, while puncture wounds resulted in 94% symptom development after 7 months of storage. Immersion into conidial suspension produced no symptoms under any conditions. No symptoms were observed in fruits at harvest or after 5 months of storage. These findings enhance the understanding of dry lenticel rot symptom development and inform future studies on managing R. mali during apple storage.