The effects of soil solarization and fumigation by 1,3-dichloropropene (D-D) or sodium methyl dithiocarbamate (metam sodium) on the soil-borne plant pathogen Phomopsis sclerotioides and soil microbial community were investigated. An experimental field at the Kanagawa Agricultural Research Institute, Kanagawa Prefecture, Japan, was treated as follows : (i) non-treated; (ii) non-treated, amended with 10 t ha^<-1> farmyard manure (FYM) ; (iii) solarized for ca. three weeks in August to September after the amendment of FYM ; (iv) solarized and fumigated with 700 L ha^<-1> D-D after the amendment of FYM ; (v) solarized and fumigated with 500 L ha^<-1> metam sodium ; and (vi) solarized and fumigated with 500 L ha^<-1> metam sodium after the amendment of FYM. Treatments (iii) to (vi) controlled the root rot of melon by the pathogen to some extent and the growth of melon plants increased using these field sanitarization treatments. About 50% of the population of total and culturable bacteria were killed by treatments (iii) to (vi), with recovery to levels prevailing in nontreated soils 35 d after cessation of the sanitarization treatments. There appeared to be changes in C-utilization (Biolog GN) profiles in the treated soils until 63 d later. However, the effects of the treatments disappeared after 193 d later. This study demonstrates that soil solarization and fumigation controlled the root rot of melon by Phomopsis sclerotioides to some extent, and that the effects of soil solarization and fumigation on soil microbial community were significant for some period, but might disappear in the following spring.
