Euston-Brown, D., Rathogwa, N & Richardson ... - DWA Home Page

1. Executive Summary
The difficulties experienced by WfW to control chromolaena and lantana in mesic savannas and sweet
grassveld stimulated the commissioning of this project. The project commenced in 2004 and used a
multi-faceted approach that included field studies, a review of international literature, and informal
discussions with managers and experts to develop a range of clearing options.
Savanna vegetation and ecosystem function is described and attempts to explain how the bush
encroachment problem is related to the process of invasion by chromolaena and lantana. A description
of the biology and ecology of the two invaders includes a summary of the traits that equip these
plants to quickly invade savanna systems. Control methods such as biological (e.g. insects and fungi),
mechanical (e.g. hand pulling, slashing, mowing and bulldozers), herbicidal (e.g. foliar spray and
cut stump treatments) and cultural (e.g. mulching, competition and fire) are detailed. The benefits
and limitations of each method are listed and practical tips for applying the treatments are provided.
Features of the ecosystem that need to be considered when choosing control methods are briefly
described into broad categories. These included various indigenous habitat types (e.g. Riparian forest,
Open savanna, mixed bushveld of rocky hillsides), land uses (e.g. game reserves, plantations, rural
areas), density/cover/height/age of aliens and seasonality.
Tables of clearing and control options are developed for four different climate scenarios and nine
different habitat/land use situations. Various situations, habitat types and seasons lend themselves to
a different combination and integration of the control options. The tables provide a tool that WfW
managers and foremen can use to choose the best approach depending on the situation. The report
also recommends an integrated approach whereby different control methods are applied in the same
area to deal with the various situations that arise in the bushveld.
The report also provides the methods and results of two field studies that were done between 2004
and 2006 in the Appendices. The results of these studies show that alien plant control is effective and
that indigenous diversity increases following the application of control measures, especially after high
summer rainfall. Working for Water and all its staff and workers can be proud of their control efforts
to date on these two invasive plants. However, control of the other invasive plant species that tend
to invade freshly cleared or burnt savanna requires urgent attention. This report strives to provide
information, data and ideas that can be used to enhance the efficiency and effectiveness of WfW
clearing teams in the control of invasive alien plants in the savannas of the east and north east part of
South Africa.
Development of a clearing protocol based on ecological criteria for Mesic Savannas and Sweet Grassveld for the Working for Water Programme