Efficacy of Chromolaena odorata control in a South African conservation forest.

CHROMOLAENA ODORATA IS A PLANT THAT invades tropical and subtropical lands, including protected areas, commercial forests and croplands around the world. The Futululu Forest Reserve in KwaZulu-Natal is situated in the latitudinal centre of the Chromolaena infestation in South Africa. In this lowland belt, the plant is increasingly invading internationally significant protected areas and large commercial tree plantations, the latter supplying the pulp and paper export industry. The Working for Water (WfW) programme's attempts to control this pest seems the most comprehensive and well-monitored anywhere in the world. We have extracted historical pre- and post-treatment Chromolaena cover information from the WfW GIS database and these have been combined with current cover data from the same management blocks at randomized sample sites. The dataset was analysed for efficacy of the control measures with statistical methods appropriate to the data. The WfW treatment programme proved effective in reducing the cover of Chromolaena but without eliminating the weed in the indigenous forest. Recommended improvements in the current WfW control methods may increase their effectiveness. However, our results suggest that only by establishing an alternative plant cover on the bare ground created by the removal of Chromolaena could control efficacy improve substantially. [ABSTRACT FROM AUTHOR]