In recent years, Almond Leaf Scorch disease (ALSD) has reemerged as a serious disease threat to almond production areas throughout California’s San Joaquin Valley. This disease is caused by the xylem-limited bacterium Xylella fastidiosa. The bacterial pathogen is transmitted by xylem feeding sharpshooters (Cicadellidae) and spittlebugs (Cercopidae).Data collected from surveys in 2003 provided us with the opportunity to sample a select number of known ALSD-affected trees on a monthly basis in an effort to monitor the seasonal fate of Xf populations. Using quantifiable, real-time PCR on the insect vectors we determined bacterial populations fluctuations over the course of a growing season relative the onset and expression of ALSD symptoms.