This opinion updates the information included in the previous EFSA Scientific Opinion concerning the
in planta control measures for Xylella fastidiosa, with a systematic review and critical analysis of
the potential treatment solutions that have been published against this pest so far. The output of this
opinion focuses on the application of chemical or biological treatments on living plants. In vitro studies,
hot water treatments, use of resistant varieties and vector control are excluded from the review. The
use of antibiotics is not considered due to the risk of antimicrobial resistance development. The use of
weakly virulent or avirulent strains of X. fastidiosa is covered in this review, although this organism is
an EU quarantine plant pest and its introduction in the EU territory is banned. Experiments were
recently conducted to assess the effect of application of zinc, copper, and citric acid biocomplex, of
N-acetylcysteine, and of ‘diffusible signal factor’ (and of its homologs). Their results showed that these
control measures were sometimes able to reduce symptoms caused by X. fastidiosa. Recent
experiments also showed that several species of endophytic microorganisms, some bacteriophages and
inoculation of weakly virulent/avirulent strains of X. fastidiosa could offer some protection against the
Pierce’s disease. However, based on the reviewed results, the Panel concludes that, although several
published experiments show some effects in reducing symptoms development, the tested control
measures are not able to completely eliminate X. fastidiosa from diseased plants. The Panel confirms
as previously stated that there is currently no control measure available to eliminate the bacteria from
a diseased plant in open field conditions