Brown root rot disease, which is caused by Phellinus noxius, is commonly found on windbreak or roadside trees in Okinawa Prefecture, including Okinawa, Kume, Miyako, Ishigaki, and Iriomote islands. Deteriorating Casuarina equisetifolia (coast sheoak) trees that exhibited the typical symptoms and signs of brown root rot were observed in windbreak stands surrounding the Okinawa Prefectural Agricultural Research Center-Nago Branch in December 2010. We applied the following three control operations at the diseased site : inserting a thin metal plate into the ground just off the affected area to shield against soil-borne infection, cutting down the coast sheoaks, and removing all underground plant residue by machine and by hand. The soil in the area was then treated with chloropicrin (trichloronitromethane). Eight month later, we planted Machilus thunbergii, Fraxinus griffithii, Araucaria heterophylla, and Cordyline sp. seedlings in the treated area. Because none of the newly planted plants and neighboring C. equisetifolia trees showed signs of infection or damage from P. noxius for 3 years after the treatment, we concluded that the disease control efforts were successful. The development of lower-cost and lower-impact operations is expected for practical control of the disease.
The composition of species and the regeneration rate of shrubs and ferns were investigated in the Japanese cedar forest heavily damaged by a fire. It seems that all of the shrubs and ferns were dead soon after the fire, but 71% of them recovered at one month after the fire. Six month later from the fire, the forest floor was thickly covered with a particular species such as Kudzu, Hyodorishogo, Yoshuyamagobo, which were rare in the non-damaged areas adjacent. It was almost plant-less just after the fire, but the forest floor was promptly covered with plants derived from buried seeds. Since about half of the trees were burned and the forest floor was disturbed by the fire, we expected there would be natural regeneration of tall tree species. However, after eight years from the fire, the density of tree seedlings of the damaged area (7150 seedlings/ha, 100 of them were taller than herbs) was not remarkably different from that of the non-damaged area (5560 seedlings/ha). Therefore, it was concluded that the fire-damaged area studied would not be covered promptly by tall trees if there is no any intervention.