Pecan Bacterial Leaf Scorch (PBLS) is causing a huge economic loss to the pecan industry of the United States. The disease is common in pecan orchards of the western pecan-producing states of Arizona, California, and New Mexico and is also found in Texas. The disease is systemic in nature and is caused by X. fastidiosa subsp. multiplex, a tedious pathogen residing in the xylem tissues of the plant and producing symptoms in late spring to summer. Due to being nonculturable and residing inside the plant throughout the year, the pathogen is very hard to detect until symptoms become evident. A qPCR-based method comprising of Xyllela antibody-coupled with carbon-nanotubes was developed for early diagnosis of the pathogen. For this purpose, X. fastidiosa antibody was coupled with carbon nanotubes and Dynabeads separately. The coupling efficiency was optimized and different magnitudes of carbon nanotubes were compared to check the coupling efficiency of Xyllelaantibody. The coupled antibody-carbon nanotube and coupled antibody-Dyanbeads complexes were compared between each other and with conventional DNA isolation based detection of X. fastidiosa subsp. multiplex from infected pecan petioles using qPCR-based DNA quantification. For this purpose, a standard curve was developed with positive control of X. fastidiosa to compare the detections from actual samples. The antibody-carbon nanotube based detection of X. fastidiosa directly from infected plant tissues was found to be the most sensitive and time-efficient method for the early detection of X. fastidiosa subsp. multiplex.