Technical Abstract: Citrus canker (caused by Xanthomonas citri subsp. citri, Xcc) is a serious disease of susceptible citrus in Florida and other citrus-growing areas of the world. The specific effects of predisposing factors for bacterial penetration of leaves are poorly characterized. Experiments were designed to investigate the effects of wind and rain (to simulate a storm), high humidity (>90%) and mild abrasion with sand (to simulate wind blow sand and debris) on infection of citrus foliage with Xcc. Exposure of leaves of Swingle citrumelo seedlings to wind (16 m sec-1) and rain (235 mm h-1) for 15 or 30 min caused significant injury and leaves developed up to two-fold as high an incidence and 10-fold as high severity compared to leaves on seedlings of non-treated control plants. The points of attachment of the lamina to the petioles were particularly susceptible to wind-induced infection with up to 25% showing disease symptoms compared to 0% for the non-treated contro. Over 80% of injured leaves had lesions associated with the site of injury. There was little or no effect of humidity >90% for 1.5 or 2.5 h on disease incidence or severity compared to the non-treated control. Mild leaf abrasion of grapefruit seedling leaves with sand increased incidence and severity of disease two-fold. Minimizing wind speed in orchards via windbreaks will reduce foliar injury and decrease canker incidence and severity.