Quantification of Fusarium oxysporum in fumigated soils by a newly developed real‐time PCR assay to assess the efficacy of fumigants for Fusarium wilt disease in strawberry plants

BACKGROUND Two soil fumigants, chloropicrin ( CP ) and dimethyl disulfide ( DMDS ), were used to control Fusarium wilt disease ( FWD ) which caused large economic losses in strawberries. The fumigants were evaluated alone and in combination in a laboratory study and in strawberry greenhouses. RESULTS Laboratory tests found that combinations of CP and DMDS indicated a positive synergistic activity on Fusarium oxysporum . A newly developed quantitative assay for F. oxysporum involving real‐time PCR was used successfully to evaluate F. oxysporum control by the fumigants; it provided similar results to the selective medium but was less time‐consuming and less labor intensive. Greenhouse trials revealed that the combination of CP and DMDS successfully suppressed the incidence of FWD and sharply reduced the population density of F. oxysporum , which significantly increased fruit branch number and maintained a good strawberry yield, higher than methyl bromide ( MB ) treatment. All of the treatments provided significantly better results than the non‐treated control. CONCLUSION This study confirms that the newly developed real‐time PCR quantitative assay for F. oxysporum was suitable for the control efficacy evaluation of soil fumigants and that the novel fumigant combination of CP and DMDS offers a promising effective alternative to MB for the control of F. oxysporum in strawberry greenhouses. © 2013 Society of Chemical Industry