Effect of oregano water on pythium density of soil and damping off disease

Pythium genus includes significant soil borne plant pathogens causing losses on many plants by root rot and damping-off diseases. Usually fungicides are used against Pythium species, but investigations on alternative methods and chemicals gained importance because of the harmful effects of pesticides on human health and environment. Plant extracts and essential oils are among the safer chemicals. Oregano plant has highly effective constituents against plant pathogens. In this study effect of oregano water was investigated against P. deliense, one of the most virulent species in our country. Oregano water obtained from Origanum onites, diluted with distilled water in 100, 80, 60, 40, 20, 10 and 5% rates was applied to soil and its effects on P. deliense population density in soil and severity of damping-off disease on bean plants caused by the pathogen were evaluated in the research. All solutions containing oregano water over 10% rate significantly decreased pathogen populations in the soil samples taken every three days after the applications, and the least pathogen density was obtained with undiluted oregano water. Mean inoculum density was 808.67 propagules per gram of soil in the control, 24 days after the applications, while it was found 367 in 100% oregano water applied soil. Similarly, emergence rate was 20% in the pathogen inoculated soil, while this rate increased with the increasing doses of oregano water and found 76.67% in the undiluted oregano water application. Root and hypocotly rot severity rates in the positive control application were 98 and 99.33%, while these rates were respectively 52.67 and 46.67%, in the 100% oregano water application. In addition, oregano water application supported shoot and root development by decreasing the negative effect of the pathogen on plant growth.