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

4.3.1.3c) Aerial spraying
Vehicle or aircraft could also apply foliar spray if the appropriate conditions prevail. This method has
been used on lantana in Australia (Clark et al. 2006). Situation of old dense monospecific stands in
remote inaccessible areas are most appropriate. Aerial Application of Bushwacker GG (bromacil)
is registered in South Africa for many indigenous species regarded as bush encroachers (Xact
Information, 2005). It is unclear as to why these two weeds do not have aerial applications registered.
The risks associated with aerial spraying on non-target native flora needs to be considered. However, if
carefully executed it can prove to be an economical method on a large scale, but only if combined with
the appropriate follow up.
Treatment Advantages (Benefits) Disadvantages (Limitations)
Aerial
spraying
• Minimises soil disturbance
• can cover vast areas quickly
• can detect isolated population in remote areas in plane
• simple contract – one man and his plane/chopper.
4.3.1.4 Cultural control – mulching, competition and fire
4.3.1.4a) Mulching
• potential negative impact on biocontrol agents
• Risk: drift onto and death of non-target plants. Remedy:
don’t use herbicides or use non-selective herbicides
• Risk: rainfall washes herbicides into rivers and is toxic to
invertebrates and fish
• Risk: heavily dependent on weather conditions and
rainfall season – mistakes possible.
• Risk: unstudied potential impacts on soil dwelling
invertebrates, fungi and other organisms in the soil.
• Risk: high chance of accidents, spillage that can result in
negative impacts on native ecosystem
We found no cases of mulching or solarisation in South Africa. This method involves using vegetative
material such as bark or wood chips or synthetic materials such as plastics to smother the soil after an
initial clearing treatment. This could help to reduce weed seedling establishment, reduce erosion and
enhance indigenous recovery. If mulch is not available then solarisation with black plastic sheeting can
be used. This method is potentially practical at small spatial scales in gardens or plots or near sensitive
areas where herbicides are not appropriate. Solarisation may be particularly useful for destroying seed
banks after clearing dense infestations, but impacts on indigenous seed banks need to be assessed. This
is a method that should be explored further before it can be recommended.
4.3.1.4b) Competition
If savanna systems are managed with fire, and the indigenous vegetation is able to persist, then this
should keep weed numbers down to manageable levels (Goodall & Naude, 1998). South African
Savanna systems are extremely resilient to disturbances, and should recover rapidly if given the chance.
If indigenous seed pools have been lost under old and dense infestations, then it may be necessary
to sow indigenous seed, especially indigenous grasses (Campbell, 2000). This is referred to as
rehabilitation. A very useful tool has been developed in South Africa that includes a dial for choosing
the appropriate grass species for sowing in different habitats (Campbell, 2000).
Development of a clearing protocol based on ecological criteria for Mesic Savannas and Sweet Grassveld for the Working for Water Programme
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