A new host record of Phacidium calderae on Citrus limon leaves, causing necrotic spots and patches, in Algeria

This study reports, for the first time, Phacidium calderae as the causal agent of necrotic lesions on Citrus limon leaves in Algeria. Symptomatic leaves showed white leathery patches with reddish margins and lenticular pustules. Fungal isolates obtained from lesions were morphologically and molecularly identified as P. calderae. Pathogenicity tests confirmed its ability to induce necrotic lesions on lemon leaves, although only in wounded tissues, suggesting low aggressiveness on citrus. However, P. calderae caused severe rot in artificially inoculated apple and pear fruit, revealing a broader host range. This finding is particularly relevant given that Phacidium lacerum was previously identified as a postharvest pathogen of apples and pears. The ability of P. calderae to infect multiple hosts raises concerns about its epidemiology and potential impact on fruit production. To our knowledge, this is the first report of P. calderae on citrus. Further research is needed to clarify its ecology, epidemiology, and interactions with other citrus pathogens.