Citrus blight was identified in two orchards at Lake Wyangan in the Riverina area of New South Wales on the basis of field symptomatology, impaired water uptake, zinc accumulation in trunk bark, plugging of xylem cells and positive serological assays (imrnunospot and Western blot) for the 12 kD blight-associated protein. Xylella fastidiosa was not detected. Spatial analyses indicated a lack of association of adjacent blighted trees at 5, 10 and 15% blight incidence. Spatial and spatio-temporal analyses confirmed this lack of adjacency and also indicated little or no associations among blighted trees over greater distances or over time. Therefore, root-graft transmission of blight was not a likely contributor to spatial processes of the blight epidemic in the orchard studied in New South Wales.