Xanthomonas campestris pv. begoniae. [Descriptions of Fungi and Bacteria].

A description is provided for Xanthomonas campestris pv. begoniae. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: On begonias. Reiger-type are most susceptible, but the disease is also reported on rhizomatous, fibrous, tuberous and winter flowering hybrid varieties (Harri et al., 1975; 54, 3343). DISEASE: Bacterial wilt and leaf spot of begonias. Symptoms first appear as small isolated spots, most easily seen on the undersides of the leaves concentrated near the margins. The spots run parallel to main veins. They enlarge, become water-soaked and eventually coalesce if conditions are very moist. The result is a soft rot often leading to premature abscission of the leaves. The stems are also affected and vascular systems invaded (Digat & Vidalie 1975; 54, 3343). Blossom infection occurs (54, 3343) and young cuttings are affected. GEOGRAPHICAL DISTRIBUTION: Rather scattered. Present in Canada, USA, St. Vincent, Brazil, parts of Western Europe, India, Japan, Iran, Australia and New Zealand (CMI Map 413, ed. 2, 1980). TRANSMISSION: The pathogen can survive in host plants during periods of latency (Digat & Vidalie, 1975) and in dead begonia leaf debris for at least 12 months (54, 878). The bacteria are carried from plant to plant at watering, either by splashing or being taken in through the roots (Harri et al., 1975). Entry into the plant is also through the hydathodes of the leaf margins (54, 3343; Digat & Vidalie, 1975), or less frequently through stomata under conditions of water congestion (Stann. 1961).