Occurrence of Colletotrichum karstii causing leaf anthracnose on blackberry ( Rubus sp.) in Mexico

Among the diseases that affect blackberries, leaf anthracnose is one of the least studied and has become increasingly important in recent years, especially in nurseries, where the responsible pathogen causes regressive stem death after pruning. In October 2023 and 2024, severe anthracnose symptoms were observed on blackberry leaves in Los Reyes, Michoacan, Mexico. The fungi isolated from diseased plants were identified by morphology and phylogenetic analyses as Colletotrichum karstii. The pathogenicity of the fungi was demonstrated by inoculating each isolate with a conidial suspension onto healthy blackberry plants, which exhibited characteristic disease symptoms after 7 days. This is the first report of C. karstii causing leaf anthracnose in blackberry in Mexico. Anthracnose in blackberry plants is an emerging disease impacting commercial fields in Mexico. Therefore, exploring its diversity and developing effective management strategies are essential.