Abstract
Epiphytic populations of Xanthomonas citri subsp. citri (Xcc) were found on symptomless grapefruit and mandarin fruits for as long as six and five days of incubation under laboratory and orchard conditions in Saudi Arabia, respectively. No differences were noticed between populations of the bacteria in the susceptible cultivar of grapefruit and the moderately susceptible cultivar of mandarin under both conditions. The occurrence of epiphytic populations was not related to subsequent appearance of symptoms on branches or leaves directly below contaminated fruits. A single chlorine treatment at 200 ppm without prewashing in water did not reduce total Xcc recovery compared to the control. However, prewashing fruit and treating with chlorine significantly reduced total bacterial recovery compared to chlorine treatment alone with both varieties.