Brachiaria

''Brachiaria'', or signalgrass, is a genus of plants in the grass family native to tropical and subtropical regions of Asia, Africa, Australia, southern Europe, the Americas, and various islands.Flora of China Vol. 22 Page 520 臂形草属 bi xing cao shu ''Brachiaria'' (Trinius) Grisebach, Ledebour, Fl. Ross. 4: 469. 1853.
Flora of China. There are over 100 species.

Some species are cultivated as forage. Some species of ''Brachiaria'' were probably first introduced unintentionally to the Americas in the colonial period, from slave ships. ''B. decumbens'' was introduced to Brazil in 1952 and ''B. ruziziensis'' in the 1960s. ''Brachiaria'' is the most widely used tropical grass in Central and South America, with about 40 million hectares planted in Brazil alone.

Biology

This genus was described in 1853. It is similar to ''Panicum'', and some authors believe ''Panicum'' is ancestral to it. It has also been confused with ''Urochloa'', and sometimes combined with it. A recent phylogenetic analysis concluded that ''Brachiaria'' and ''Urochloa'' are a monophyletic group, along with ''Eriochloa'' and ''Melinis'', and that further molecular and morphological work is needed to establish clear relationships. In the meantime, ''Brachiaria'' and ''Urochloa'' plants are usually not difficult to distinguish from one another.

''Brachiaria'' are annual or perennial grasses, most lacking rhizomes. The inflorescence is a branching panicle, and the plant reaches about a meter in height.Watson, L. and M. J. Dallwitz. (2008)
''Brachiaria''.
The Grass Genera of the World. Retrieved 7 November 2011. The plants are bisexual and the flowers are fleshy, with 3 anthers.Clayton, W. D., et al. (2002 onwards)
''Brachiaria''.
GrassBase - The Online World Grass Flora. Some species have a prominent vein in the center of the leaf. ''Brachiaria'' are C₄ species and can tolerate drier conditions and more light exposure than some other plants.

Ecology and conservation

''Brachiaria'' can grow in many environments, from swamps to shady forest to semidesert, but generally do best in savannas and other open tropical ecosystems such as in East Africa. In Angola, ''B. brizantha'' grows on termite mounds and in the ecotone between grassland and woodland habitat.Estes, R. D. and R. K. Estes. (1974). The biology and conservation of the giant sable antelope, ''Hippotragus niger variani'' Thomas, 1916. ''Proceedings of the Academy of Natural Sciences of Philadelphia'' 126, 73-104. In the Kora National Reserve in Kenya, ''Brachiaria'' dominates the ground layer along with ''Aristida''. In India, the native ''B. ramosa'' is an important food source for the Eurasian collared dove (''Streptopelia decaocto'') and ''Brachiaria'' species are forage for other local herbivores.

In North America, the native ''B. platyphylla'', broadleaf signalgrass, grows after heavy rains and then reproduces prodigiously and quickly, sometimes becoming a weed.

Wide expanses of the tropics, especially the Neotropics, have been converted to ''Brachiaria'' pasture to support livestock. In Brazil, 80 million hectares of native habitat have been planted with African grasses, mostly ''Brachiaria''.

Introduced species such as ''Brachiaria'' grasses can degrade habitat and compete with native species. In Northern Australia, the exotic ''B. decumbens'' competes with the native tree '' Alphitonia petriei'' by inhibiting the growth of seedlings, slowing the conversion of abandoned pastureland to natural forest. In the Paragominas area of Brazil, however, native forest outcompetes cultivated stands of ''Brachiaria'' and other exotic forage grasses, and ranchers struggle to maintain pasture cover. Native species may also utilize exotic ''Brachiaria'' as a food resource, such as the rock cavy (''Kerodon rupestris''), a native rodent of the caatinga.

Cultivation

''Brachiaria'' is the single most important genus of forage grass for pastures in the tropics. ''Brachiaria'' cultivars can grow in infertile and acidic soils. Brazil is the leading user and producer of ''Brachiaria'' seeds in the Americas.

Mexico has put effort into improving its trade in ''Brachiaria'' cultivars, and the grass is thought to have made a positive impact on its milk and beef industries.Holmann, F., et al. (2004)
Impact of the adoption of ''Brachiaria'' grasses: Central America and Mexico.
''Livestock Research for Rural Development'' 16, Art. #98. Central American countries have also increased seed sales and area planted in the grass. The annual growth rate of seed sales in 2009 was 32% in Mexico, 62% in Honduras, 45% in Nicaragua, 39% in Costa Rica, and 54% in Panama. The area planted with ''Brachiaria'' during this period was about 6.5% of the total surface of permanent grasses in Mexico, 12.5% in Honduras, 1% in Nicaragua, 18.7% in Costa Rica, and 0.1% in Panama.

Agricultural pests of ''Brachiaria'' include spittlebugs, leafcutter ants, and mound-building termites.

Other insect pests include:

*shoot flies ''Atherigona oryzae'', ''Atherigona pulla'', and ''Atherigona punctata''
*caseworm '' Paraponyx stagnalis''
*red hairy caterpillars ''Amsacta albistriga'' and ''Amsacta moorei