DISTRIBUTION, IMPACT AND MANAGEMENT OF CHROMOLAENA ODORATA IN SOUTHERN AFRICA

Abstract

Chromolaena odorata continues to spread through the subtropical regions of southern Africa and to become denser where it is already present, leading to major vegetation changes. The manner of its introduction remains uncertain, but probably occurred directly from the West Indies, as the southern African biotype differs from that invasive elsewhere in the world. First recorded as naturalised around Durban, South Africa in the 1940s, chromolaena spread rapidly throughout the coastal region of KwaZulu-Natal province between the 1950s and 1980s. In the past two decades it has reached other provinces: southwards into the Eastern Cape and northwards into Mpumalanga and Northern Province, while the neighbouring countries of Swaziland, Mozambique and possibly Zimbabwe have also been invaded. The southern African biotype of chromolaena is likely to be spreading northwards towards Tanzania, while the Asian biotype is already present on the Indian Ocean island of Mauritius. In South Africa, chromolaena mostly threatens conservation areas, but also impacts negatively on forestry, pastoral agriculture and other land-uses. Although public awareness of the weed is now much higher than it previously was in this country, its spread has proceeded largely unchecked until recently. Few private landowners were committed to clearing chromolaena in the early stages of invasion, or have had the resources to clear it later. Several herbicides are registered for use on chromolaena, and integrated control