Characterization of emerging <i>Pestalotiopsis</i> sensu lato causing foliar blights on conifers in Taiwan and a preliminary assessment of fungicide susceptibility

Pestalotiopsis sensu lato species have gained attention as emerging primary pathogens on economically important crops, shifting from their previous roles as weak pathogens, saprobes, or endophytes. Coniferous trees in Taiwan have recently shown fungal infection symptoms, prompting further investigation. Field surveys revealed leaf spots and blight on six cultivated conifer species namely, Calocedrus formosana, Chamaecyparis formosensis, Chamaecyparis obtusa var. formosana (Cupressaceae), Podocarpus costalis, Podocarpus macrophyllus, and Podocarpus nakaii (Podocarpaceae). This study aimed to identify the causal fungal taxa and assess their fungicide sensitivity. A total of 66 Pestalotiopsis sensu lato isolates were recovered from diseased tissues. Phylogenetic analyses using ITS, tef1-α, and tub2 sequences, combined with morphological characteristics, revealed ten taxa including six species and four tentative clades from genera Pestalotiopsis, Pseudopestalotiopsis, and Neopestalotiopsis. Six species (P. neolitseae, P. parva, P. subshorea, P. trachycarpicola, Pseudopestalotiopsis elaeidis, and Ps. ixorae) represent first reports on these conifer hosts. Neopestalotiopsis and Pestalotiopsis were most frequently isolated, while Pseudopestalotiopsis was less common. Fungicide assays revealed that fluazinam exhibited the strongest and broadest antifungal activity, while other fungicides showed species-specific efficacy. These results highlight the importance of accurate species identification for effective disease management and fungicide selection. This study highlights Pestalotiopsis sensu lato emergence as conifer pathogens in Taiwan and underscores the need for integrated management strategies with field-based fungicide evaluations.