Increasing of treatment time with ozone from 5 to 15 minutes resulted in an increased resistance to decay (figure 1). Use of ozone with 2500 and 5000 concentrations could control Botrytis cinerea in grapes up to 50%. Use of ozone with 5000 mgl concentration in strawberry has been effective in reducing fungal and yeast infections.Ozone can be effective in stimulating the production of phytoalexins within the plant,which increase the plant's resistant to decadence accordingly and have high antioxidant role.