Eradication of Rosellinia necatrix Prillieux on Japanese apricot by soil solarization

White root rot fungus, (Rosellinia necatrix Prillieux) was eliminated from both naturally infected root segments and inoculated shoot segments buried in non-sterilized soil when the soil temperature was maintained at 35°C for 12 hours per day for 4 days. At a soil temperature of 32°C, 7 days were required for the elimination of the fungus from shoot segments. In a Japanese apricot orchard located in the southern area of Wakayama Prefecture, Minabe-cho, Hidaka-gun, Japan, the effects of solarization on the eradication of R. necatrix in mulched soil on vinyl sheets (3×3 m) were evaluated for 2 months from late July in 2006, 2007, and 2008. The pathogen, which was inoculated into shoot segments buried at depths of up to 80 cm at the center of the site and at depths of up to 60 cm at a distance of 110 cm from the center of the site was eliminated after 2 months of solarization, although the rate of elimination was lower at the edge of the site. The depth of shoots in the soil almost eliminated the pathogen when soil temperature above 32°C was recorded for at least 7 consecutive days. In contrast, the pathogen was not eliminated when the temperature of the soil was observed to be not above 32°C for at least 7 consecutive days; thus, the integration time of the soil temperature can estimate the success of elimination of the pathogen. Therefore, in areas that, in summer, show weather conditions similar to those of the orchard in which this field experiment was performed, soil solarization may be effective in the eradication of white root rot fungus in soil at the plot from which the affected Japanese apricot tree was removed.