Abstract
The effect of fumigation with methylisothiocyanate (MITC) against some soil-borne plant pathogens was examined in a polypropylene bottle. The soil-borne pathogens used were Rhizoctonia solani, Fusarium oxysporum f. sp. lycopersici races J1 and J2, F. oxysporum f. sp. fragariae, Verticillium dahliae, Colletotrichum fragariae, Mycosphaerella melonis, Pseudomonas solanacearum, Agrobacterium tumefaciens biovars 1 and 2 and A. rhizogenes biovar 1.
When conidia and mycelia of the pathogens were exposed to MITC in a polypropylene bottle, conidia of F. oxysporum, V. dahliae, C. fragariae and M. melonis were killed at 3mg/l for 24hr, 1-2 mg/l for 48 hr, 1mg/l for 72hr and 0.5-1mg/l for 96hr. P. solanacearum and A. tumefaciens were killed at 2mg/l MITC for 24hr and 1mg/l for 48-96hr. R. solani was killed at 0.5mg/l MITC for 24-48hr and 0.25-0.5mg/l for 72-96hr. In the case of chlamydospores, F. oxysporum f. sp. lycopersici races J1 and J2 were killed at 16-20mg/l MITC for 24hr, 10mg/l for 48hr, 8mg/l for 72hr and 6-8mg/l for 96hr. F. oxysporum f. sp. fragariae was killed at lower concentrations. Sclerotia of R. solani were killed at 4mg/l for 24hr and 1mg/l for 96hr.
The effect of MITC depended on the species of fungi and bacteria and the organs of the fungi. Chlamydospores of fusaria were killed by the exposure to MITC 7-8 times of concentrations more than conidia and mycelia. The minimum concentration of MITC to kill the fungi and bacteria was in relation to the duration of exposure.
Fusaria and A. tumefaciens in a clad were put into soil 15cm deep and exposed to MITC. MITC was effective to the pathogens when a diameter of a clad was 1.5cm or pathogens were put directly into soil, but not effective when a diameter of a clad was 2.5cm or more.
It was clear that the effect of MITC against the pathogens in the soil was greatly influenced by the size of a clad.
