Rust on the Tropical Pasture Grass Brachiaria humidicola in South America. J. M. Lenné, Centro Internacional de Agricultura Tropical (CIAT), Apartado Aereo 6713, Cali, Colombia. Plant Dis. 74:720. Accepted for publication 6 April 1990. Copyright 1990 The American Phytopathological Society. DOI: 10.1094/PD-74-0720A.
A rust, caused by Uromyces setariae-italicae Yosh., is reported as a serious pathogen of the pasture grass Brachiaria humidicola (Rendle) Schweick. in humid regions of tropical South America. First observed by me in South America (Brazil) in 1981 and identified by the International Mycological Institute in England, it has since been found in Colombia, Ecuador, and Peru. Recently, yield losses of up to 100% were measured in Napo and Puyo, Ecuador. The rust produces cream-colored pustules containing yellow urediniospores on both leaf surfaces, resuling in leaf necrosis. In addition to B. humidicola, the rust has been previously recorded on 28 species of Brachiaria, including B. brizantha, B. decumbens, and B. dictyoneura, as well as species of the grasses Eragrostis, Eriochloa, Melinis, Panicum, Paspalidium, Pennisetum, Setaria, and Urochloa throughout eastern Africa and from several countries in Asia, the Caribbean, Central America, Australasia, and Oceania, as well as South America. A large collection of species of Brachiaria is currently being evaluated by CIAT for resistance to U. setariae-italicae in Carimagua, Colombia. This rust is the first important disease encountered in South America on a tropical pasture grass introduced from Africa.