Bucar Indjai1, Maria Cristina Duarte2, Filipa Monteiro2,3, Cristina Máguas2 and Luís Catarino2
1CEATA/INEP – Centro de Estudos Ambientais e Tecnologia Apropriada, Instituto Nacional de Estudos e Pesquisa, Bissau, Guinea-Bissau
2Centre for Ecology, Evolution and Environmental Changes (cE3c), Faculdade de Ciências, Universidade de Lisboa, Campo Grande, 1749-016 Lisboa, Lisbon, Portugal
3LEAF- Linking Landscape, Environment, Agriculture and Food, Instituto Superior de Agronomia (ISA), University of Lisbon, Lisbon, Portugal
e-mail: email@example.com (Cristina Máguas)
Chromolaena odorata (L.) R. M. King & H. Rob (Siam weed, Asteraceae) is recognized as one of the worlds worst invasive tropical plants. It is a perennial herb or shrub, native to North and Central America that became invasive throughout the tropical regions of Africa, Asia and Oceania. Two biotypes are recognized in Africa (the Asian/West African biotype and the Southern African biotype). In West Africa, after the accidental introduction in 1937 in Nigeria, it spread to other countries in the region, presently occurring in the upland zones of almost all countries.
In Guinea-Bissau, the presence of Siam weed was recently documented for the first time, but its presence seems to date back to the end of 1990’s. At first, the species was recorded in the south-western part of the country, probably arising from Guinea Republic, in which its presence was documented for several years. Data gathered in the last months point to a considerable spread of C. odorata in Guinea-Bissau, from south to the north, but this seems to be in an early phase. With this work, we aim to provide more systematic information of this early invader, the species habitat characteristics, and introduction time and history
Although the presence of the species was noted for several years, it has only recently expanded and become problematic. Siam weed is said to be invasive in young fallows, hampering land clearing, and in the last few years it has been noted to “suffocate” other plants becoming troublesome for several crops. Since the country is suitable for the Asian-West African biotype, it is likely that the invasion will continue. Therefore control measures are needed in order to prevent its expansion and avoid harmful consequences.