Disease Note.

Association of Xylella fastidiosa with Leaf Scorch and Decline of Live Oak in Florida. R. J. McGovern, University of Florida, Southwest Florida Research and Education Center, Immokalee 33934. D. L. Hopkins, University of Florida, Central Florida Research and Education Center, Leesburg 34748. Plant Dis. 78:09241. Accepted for publication 11 May 1994. Copyright 1994 The American Phytopathological Society. DOI: 10.1094/PD-78-0924B.

Bacterial leaf scorch, caused by Xylella fastidiosa Wells et al, has been reported in southern red oak (Quercus falcata Michx., laurel oak (Q. laurifolia Michx., and water oak (Q. nigra L.) in Florida (I). During the autumn of 1992, decline, marginal leaf necrosis, and branch dieback were observed in three live oak trees (Q. virginiana Mill.) from two landscape sites in southwest Florida. X. fastidiosa was detected in vacuum extracts of stems from the three trees by enzyme-linked immunosorbent assays (ELISA) and was cultured from one tree using PW medium. Spring growth of infected trees was delayed. Some branches defoliated and then produced a flush of distorted leaves with necrotic tips. Extensive, rapid large-branch dieback subsequently occurred in one of the infected trees. During autumn 1993, nine additional symptomatic live oaks from eight separate landscape, native, and nursery sites in southwest and west central Florida also tested positive for X. fastidiosa by ELISA and polymerase chain reaction procedures (2). This represents the first report of X. fastidiosa infection of Q. virginiana.