Data are from three experimental trials examining pre-existing water stress on Xylella fastidiosa infections and possible associated shifts in host chemistry, including free sugar, amino acid, and phenolic compound measurements. Trials A and B were utilized in the manuscript, whereas Trial C was data from an experiment whereby the water stress treatment was not significant enough to affect plant physiology or bacterial progression (but included for completeness). Predawn water potentials and photosynthesis were provided for trial B to show methodology worked (and for trial C to show the failure to reach water stress).