The grape strain of Xylella fastidiosa (Xf) causes Pierce's disease (PD) in grapevines and is transmitted by sharpshooter insects. The most efficient vector for transmission is the glassy-winged sharpshooter (GWSS), Homalodisca coagulata. Symbiotic control employs mutualistic bacteria to deliver anti-Xf compounds to disrupt transmission of the pathogen to new host plants. Alcaligenes xylosoxidans var. denitrificans (Axd) is a prime candidate for control of PD because it inhabits the foregut of GWSS and the xylem of plants and has access to the pathogen, Xf. Registration of Axd as a microbial pesticide requires the ecology of Axd to be determined along with any side-effects. Candidate toxins to be expressed by Axd disrupt disease transmission. Axd colonized and traveled within 6 host plants, reaching the highest titers in lemon. Axd colonized the foregut region of two alternate Xf-vectors, the blue green and smoke tree sharpshooters, and was not identified in predatory arthropods that fed on Axd-positive GWSS.