First report of the oil palm disease fungus Marasmius palmivorus from Taiwan causing stem rot disease on native Formosa palm Arenga engleri as new host.

Basidiomata were found on dead stems of wild native Formosa palm (Arenga engleri) in Taiwan. The fungus was identified based on morphology and internal transcribed spacer sequence comparison as the oil palm pathogen Marasmius palmivorus. A pathogenicity test with cultivated mycelium of M. palmivorus positively produced disease symptoms and death of non-wounded Formosa palm tree seedlings under excessive moisture conditions. These results indicate that mycelial inoculum may be more important for pathogenesis than spore inoculum and that the fungus does not require wounds for entry into the plant. Host records in the literature are critically revised. The extended geographical and host distribution indicate a greater risk by M. palmivorus in palm plantations than hitherto anticipated. SIGNIFICANCE AND IMPACT OF THE STUDY: Certain palm species are susceptible to disease caused by Marasmius palmivorus, particularly in oil and coconut palm plantations in tropical countries. Hitherto, there is no published information on the morphology and pathogenicity of the species in Taiwan.