Abstract
Effective control of white root rot using fungicides (fluazinum and dazomet) or a soil conditioner containing microorganisms (including the fungi Tricoderma spp.) when replanting orchards of Japanese pear was investigated in a field experiment. Fluazinum was more effective than the two other materials. However, 3 of the treatments applied also induced some symptoms with leaves that were pale, miniature or crimped and the growth of new shoots delayed or occurred and then withered. In an another experiment using only fluazinum, the occurrence of these symptoms was investigated in relation to the physical characteristics of soil and how the treatments were applied. In this experiment, these symptoms also occurred when the treatment applied was only water and not a solution. Moreover, these symptoms did not occur when the soil was piled up without stirring. The soil of treatments that did not produce symptoms remained relatively soft and contained lots of air. From this research it was inferred that the symptoms were not caused by the products used but were due to the solutions (or water) and soil being artificially mixed with strong stirring to spread the treatments into the clay soil.
