Guignardia citricarpa . [Descriptions of Fungi and Bacteria

Abstract

Abstract A description is provided for Guignardia citricarpa . Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: On Citrus spp. Also recorded in a non-pathogenic form on many other hosts in the following families: Anacardiaceae, Aquifoliaceae, Bignoniaceae, Burseraceae, Cunoniaceae, Dioscoreaceae, Gramineae, Lauraceae, Leguminosae, Liliaceae, Lythraceae, Magnoliaceae, Myrtaceae, Orchidaceae, Passifloraceae, Proteaceae, Rosaceae, Rutaceae, Solanaceae, Sterculiaceae, Theaceae (29: 208; 43: 1922a; Herb. IMI). DISEASE: Black spot of citrus. Kiely (1949) described 3 types of fruit lesion: Hard spot and shot-hole spot numerous, at first circular, brown with slight depressions, later more depressed in the centre which turns grey-white, margin black and surrounded by a ring of green rind tissue; Freckle spot develops after hard spot phase with abundant lesions, small, deep organge to brick red, finally brown, lacking a green ring, Virulent spot , irregular, confluent, rapidly spreading, black in the centre where pycnidia are produced, brown nearer the edge, finally brick red at the periphery forming the margin of the sunken lesion. McOnie found field temperatures affected symptom expression (44: 1556b). Also occurs on leaves, twigs and flowers of citrus and other hosts, often as latent infections. GEOGRAPHICAL DISTRIBUTION: Widely distributed on a large number of hosts. Countries where the fungus has been reported as a pathogen of citrus fruit in the field are designated below with an asterisk: Africa (? Egypt, Kenya, Mozambique, Nigeria, *Rhodesia, *South Africa, Uganda), Asia (Ceylon, *China, *Formosa (Taiwan), Hong Kong,? India, *Indonesia, Iran, Israel, *Japan, Korea,? Malaya, Okinawa,? Pakistan,? Philippines,? Singapore,? Thailand,? Vietnam); Australasia & Oceania, (*Australia,? Fiji Islands,? Hawaii, New Hebrides), Europe (Sicily, Spain, U.S.S.R. (Republic of Georgia)); North America (United States (Florida)); Central America and the Caribbean (Honduras, Jamaica, Trinidad); South America (*Argentine, *Brazil, *Peru, Venezuela). (CMI Map 53, ed. 3, 1961; 29: 208; 44, 701; Herb. IMI). TRANSMISSION: By air-borne ascospores from perithecia produced on cirrus leaf litter (43, 1922b). Conidia produced from pycnidia require water droplets for emergence and dispersal. They play a minor role by contributing to the infection of low hanging fruit. Mycelium in latent infections of citrus leaves remains viable up to 18 days and may be detected when the leaves are incubated at 30°C (Kiely, 1949). Nursery trees may also carry latent infection into other citrus growing areas (Kiely, 1949; Wager, 1953). Wounds on fruit made by insects may also provide infection courts (16: 247, 22: 19).