Detection and Vertical Distribution of White Root Rot Fungus in Forest Soils

Abstract

Detection and vertical distribution survey of the white root-rot fungus, Rosellinia necatrix (Hart.) Berl. were conducted in four forest soils in Hyogo and Kyoto Prefectures. These forests are located adjacent to mulberry fields which had been established on newly opened forests and the mulberry trees are sufferring from the white root rot disease. Whether the fungus was present or not in the forest soils was tested by examining the typical mycelium strands adhering to plant remnants and also by baiting method. In the latter method, bundles of mulberry and copse twigs, 30cm long, were buried to the depth of 20cm, and after a month or two the bundles were removed and examined for the colonization of the fungus. Under forest conditions, the fungus grows and survives saprophytically on partially decomposed plant debris in the F-, H-, and A₁-layeres. The fungus inhabits to depths of one to five cm from the top of A-layer. In cases where the A-layer developed well into a thick layer, the fungus grew densely throughout the A₁-layer; on the contrary, in cases where the A-layer developed only faintly, the fungus appeared in F- and H- layers and the amount of mycelial strands remained small.