The impact of two active ingredients of plant essential oils on the causative agent of apple and pear fire blight disease

Erwinia amylovora, the cause of apple and pear fire blight disease, is one of the main factors limiting the production of these fruits in the world. Since only a limited number of copper compounds have a protective effect in controlling this disease, increasing attention has been paid to investigating the effect of plant essential oils on this pathogen.

The effect of different concentrations of carvacrol (the active ingredient of thyme, oregano, etc.) and trans-anethole (the active ingredient of fennel essential oil) on the growth of E. amylovora colony, was investigated in laboratory conditions, and their minimum inhibitory concentration (MIC), and minimum bactericidal concentration (MBC) were determined. The inhibitory effect of MIC of these substances alone and the mixture of one-half of their MIC and MBC concentrations was investigated by disc method on nutrient agar medium on the growth of E. amylovora colony. The effect of the three best mixing ratios of these materials on the fruit tissue of the pear Spadona variety was evaluated on the severity of fire blight disease.

Carvacrol and trans-anethole both had antibacterial effects against E. amylovora, but the effect of carvacrol was greater than the other. Mixing carvacrol with trans-anethole increased its effectiveness. Among the three mixing ratios, 47 µg/ml of carvacrol + 141 µg/ml of trans-anethole caused the greatest reduction in disease severity in pear fruit tissue.

The use of a mixture of carvacrol and trans-anethole can be considered for the management of fire blight disease.