Last updated: 17th November 2009
When dealing with invasive species there are three main ways considered
for controlling them; physical, chemical or biological. Physical control is where plants
are manually or with the aid of machinery removed from the site. Chemical involves the
use of herbicides to kill the plants. Biological control is the use of another organism
that naturally attacks the plant to be released to try and kill the whole population of
plants. Biological control involved very long term experiments and is extremely expensive
in the initial stages and without any guarantees of success. For this reason biological
control was not included as part of the project, the main emphasis was on the use of herbicides,
although removal was also used as several sites.
Each methodology has both positive and negative sides which must be weighed out for each
situation. Herbicide treatments are generally considered more efficient and cost-effective
than other methods (Carlile 2006; Motooka et al. 2002). The disadvantage of using chemicals is
the potential negative impacts on the environment, affecting not only the target species but
also other species in the neighbouring area. Physical removal can be largely labour intensive,
meaning it could be hugely costly, it can in the case of Gunnera be difficult as it reproduces by
vegetative means, the disposal of material removed will be problematic. But if feasible it is less
damaging to the environment and an area will be ready to be used straight away.
A set of experiments were carried out over several years to look at the possibility of
using herbicide as a means to control Gunnera.
1. Greenhouse Experiment- "Concentrations of RoundUp"
Three different concentrations of the herbicide RoundUp were used to find out if the recommendations by
the manufacture were adequate or if a stronger concentration is required. The following table shows
the concentrations used.