Effect of eight essential oils on bacterial canker disease in citrus

 Citrus bacterial canker caused by Xanthomonas citri subsp. citri is an economically important disease in many tropical and subtropical countries. Several pathotypes of this pathogen have been described which, in addition to certain genotypic features, are distinguished above all by their geographical origin and their host range. Citrus bacterial canker disease is wide spread in Iran and a major threat to the production of Mexican lime (Citrus aurantifolia). Therefore, management of citrus canker is inevitable in citrus growing areas where citrus canker has been established. Application of copper-based bactericides is a standard control measure for management of citrus canker worldwide. Therefore, their long-term use leads to the development of resistant isolates. Plant extracts and essential oils with an antimicrobial effect have become particularly important as an environmentally friendly method for the treatment of plant diseases. Many researchers have recently focused on studying plant extracts and essential oils that contain antimicrobial compounds. 

 The present study was carried out on the antibacterial effect of ‌Common yarrow (Achillea millefolium), Ginger (Zingiber offcinale), Golden marguerite (Anthemis tinctoria), Fennel (Foeniculum vulgare), Common sage (Salvia officinalis), Gum tragacanth (Astaragalus gossypinus), Summer savory (Satureja hortensis) and True cardamom (Elettaria cardamomum) against two pathotype of Xanthomonas citri subsp. citri under laboratory and greenhouse conditions. 

 All essential oils have an inhibitory effect on multiplication of Xanthomonas citri subsp. citri. The antibacterial test results showed that the essential oils of Ginger and True cardamom strongly inhibited the growth of Xanthomonas citri subsp. citri pathotype, especially the pathotype A*, whereas other essential oils showed moderate to weak activities. 

 The essential oils of these eight plants, especially ginger and cardamom, have good potential for the management of citrus bacterial canker.