Brown Root Rot of Trees Caused by Phellinus noxius in Windbreaks on Ishigaki Island, Japan. Incidence of Disease, Pathogen and Artificial Inoculation.

Abstract

Extensive wilts of trees have recently occurred in the windbreaks at Okinawa Branch of the Tropical Agricultural Research Center in Ishigaki Island, Okinawa, Japan. Dead or declined trees were observed at 43 points, the total number of dead and declined trees was over 200 and total length of damaged windbreaks was 515m, in about 11% of the total length of windbreaks. Roots of dead and declined trees were collected and many fungus cultures were isolated from them. Most isolates had the following common cultural characteristics: no clamp connections on septa, staghorn-like hyphae and arthroconidia. Two cultures isolated from tissue of diseased trees were artificially inoculated into saplings of Podocarpus macrophyllus. Nine saplings were killed out of 19 inoculated saplings within 13 months and the fungus was reisolated from the dead saplings. As the isolates were considered to be a hymenomycetous fungus, fungal fruiting bodies were collected from windbreaks and from nearby and cultures were isolated from the collected fruiting bodies. One of cultures isolated from the collected fruiting bodies coincided in cultural characteristics with the isolates from dead and declined trees. The fruiting body from which this culture was isolated, was identified as Phellinus noxius (Corner) Cunningham. Taxonomic study revealed that Ph. sublamaenis (Lloyd) Ryvarden, published as a prior name for Ph. noxius, is a synonym of Ph. lamaensis. The fungus reported as Ph. lamaensis by Yasuda from Bonin Island of Japan in 1916, was identified as Ph. noxius.