Study of the efficacy of wood vinegar on soil-borne pathogenic fungi of green house-cucumber

Soil-borne fungal diseases cause considerable damages to greenhouse cucumber in many greenhouses in Iran where considerable amounts of fungicides are being used for their control. Wood vinegar (also called pyroligneous acid) produced through the natural process of wood carbonization, is a liquid obtained from distillation and compression of the gas resulted from wood burning under airless conditions. The antimicrobial effects of wood vinegar have been shown on a few number of plant pathogens. In this study, the antifungal effect of wood vinegar produced in Iran, was studied on the control of several fungal pathogens of greenhouse-cucumber including: Fusarium oxysporum f. sp. radicis- cucumerinum, Pythium aphanidermatum, Verticillium dahliae, Sclerotinia sclerotiorum, Phytophthora drechsleri and Rhizoctonia solani both in vitro and in situ conditions. The inhibitory effect of wood vinegar was investigated on each of the pathogens in the presence of different concentrations (0.75, 0.5, 0.37, 0.25, 0.125, 0.05, 0.025 and 0 percentage v/v) of the vinegar. In order to study the effect of volatile metabolites of wood vinegar, a similar test was conducted on these pathogens using segmented Petri-dishes. In greenhouse experiments, three concentration of wood vinegar was used one day after transplanting and every 2 weeks up to three times on cucumber plants inoculated with each of the pathogens. The experiment was performed in completely randomized design with five replicates. The efficacy of wood vinegar was assessed through measurement of disease severity, wet and dry weight of roots and shoots, as well as root length and shoot height. Volatile and non-volatile metabolites in wood vinegar inhibited significantly the mycelial growth of F. oxysporum f. sp. radicis-cucumerinum, P. aphanidermatum, V. dahliae، S. sclerotiorum, P. drechsleri and R. solani. The maximum inhibitory effect was observed for both volatile and non-volatile metabolites at 0.75% and 0.5% concentration of wood vinegar.In green-house experiments, all concentrations of wood vinegar reduced the disease incidence while, increased the growth parameters of cucumber plants. The maximum disease control was observed for V. dahliae, F. oxysporum, P. aphanidermatum, R. solani and P. drechsleri at 0.125%, 0.25%, 0.125%, 0.25 and 1% concentration of wood vinegar respectively. This study showed that wood vinegar has the potential to control soil borne fungal pathogens as well as to increase plant growth parameters of cucumber grown in green houses.