Xylella fastidiosa causes significant losses in many economically important crops. An efficient pathogen detection system is critical for epidemiology studies, particularly when large sample size is involved. In this study we report the development of immunomolecular assays like Immmunocapture-PCR and Immuno-PCR for direct detection of X fastidiosa without DNA isolation. Whereas the reactivity of ELISA and PCR ranged from 10(6) to 10(4) bacterial cells, the IC-PCR sensitivity was up to 10(3) and the detection limit of I-PCR was up to 10(1) bacterial cells. These methods can use either plant sample extracts or cultivated media. and show no cross reaction for any other endophytic citrus-bacteria. Therefore, IC-PCR and I-PCR assays provide an alternative for quick and very sensitive methods to screening X fastidiosa, with the advantage of not requiring any concentration or DNA purification steps while still allowing an accurate diagnosis of CVC. (C) 2008 Elsevier B.V. All rights reserved.