Scientists demonstrated that a formulation of eucalyptus essential oil protects almond plants from X. fastidiosa, although it does not eliminate the pathogen. In a paper published on Frontiers in Plant Science, a group of Spanish researchers, including the BeXyl work package leader Emilio Montesinos from the University of Girona, presented the results of the application of such formulation to X. fastidiosa infected almond plants in greenhouses, by different strategies (endotherapy and soil drenching, preventive, curative or a combination of both).

With all the methods, the applications reduce the symptoms of Almond Leaf Scorch, the disease caused by X. fastidiosa in almonds, and are associated with decreased pathogen levels in treated plants. The severity of infections decreased “with efficacies varying from 50 to 70%,” the scientists report. However, the bacterium was still present in the plant.

The tested formulation “acts by a dual mechanism, directly against the target plant pathogenic bacteria and indirectly by eliciting defense responses in the host plant,” scientists write. That feature and the efficacy of different application methods might pave the way to design new biocontrol products.

Eucalyptus oil is known for its antimicrobial activity, and the use of eucalyptus preparations to fluidify bronchial secretions in humans and animals is widespread. Previous studies proved the effectiveness of specific plant extracts or essential oils for controlling specific plant pathogens and pests, mainly in laboratory tests. Given that X. fastidiosa clogs the xylematic vessels, those conveying the raw sap from the roots towards the rest of the plant, scientists are exploring the hypothesis that eucalyptus can have on the infected plants a similar “de-clogging” effect as in humans, helping to clear the xylem.