Alternative control of bacterial leaf blight of eucalypt using essential oils

Abstract

Bacterial leaf blight, attributed to Xanthomonas citri pv. eucalyptorum comb. nov., poses a significant threat to eucalypt nursery and field conditions in Brazil, resulting in substantial annual losses. While various disease management practices are employed, the quest for alternative control methods and environmentally friendly antimicrobial agents remains imperative. Thus, this project was developed to assess the potential efficacy in vitro of essential oils derived from tea tree (Melaleuca alternifolia), copaíba (Copaifera officinalis), and lemongrass (Cymbopogon spp.) against X. citri pv. eucalyptorum. The sensitivity of the bacteria to these oils was examined via antibiogram testing, with each antibiogram subjected to different oil dilutions (6.25 %, 10.00 %, 12.50 %, 25.00 %, 50.00 %, and 100.00 %). Inhibition zones were assessed to determine the inhibitory capacity of each compound on microbial growth, and statistical analysis was conducted using the Mann-Whitney test. Copaíba oil did not exhibit any inhibitory effect on the pathogen growth in vitro. Conversely, both lemongrass and tea tree oils displayed inhibitory effects on the target bacteria, with a minimum inhibitory concentration of 12.50 %. Furthermore, no significant distinctions were observed between the utilization of 12.50 % and 25.00 % concentrations of tea tree, neither between 25.00 % of lemongrass or 50.00 % of tea tree dilutions. These findings may pave the way for new strategies in pathogen management.

Keywords

• Plant Pathology. Xanthomonas citri pv. eucalyptorum comb. nov. Eucalyptus spp. Disease management.