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

flower and set seed. To apply foliar spray to taller/older plants they first need to be slashed and the
fresh regrowth is then sprayed.
Treatment Advantages (Benefi ts) Disadvantages (Limitations)
Foliar spray • relatively quick and
requires less labour
• as herbicides are very
diluted (usually 1-2 %
concentration with water)
may use less herbicides
• if correctly applied it is
highly effective
• many small teams can
cover large areas relatively
quickly
• Requires access to good quality clean water
• Heavy backpacks – worker fatigue
• Mixing of herbicides and equipment preparation requires technical proficiency and
takes time.
• potential negative impact on biocontrol agents
• if applied to older plants it requires slashing first and then spraying regrowth – two
operations (more time more expensive)
• 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.
• Risk: health hazards
Practical tips for foliar spray applications: 1) timing – tune into the local weather patterns, make sure
that plants are growing actively or regrowth is “ready” for foliar spray, don’t spray if dew or rain drops
are on the leaves – use another
control method until they are
dry 2) training – make sure
users are properly trained 3)
use clean water – dirty water
clogs equipment, 4) preventing
spray drift – only spray in
suitable weather conditions -
milder temperatures and higher
humidity are best. Consistent
very light winds (5-15 kph)
blowing away from risk areas
(e.g. sensitive natural habitat,
crops, settlements) is preferable
5) do spot spraying – because
of the risks and unforeseen
impacts of herbicides on the
environment avoid blanket
spraying an entire area if
possible by integrating with
cut & treat and hand pulling
where possible. 5) dust on
leaves can prevent absorption
of the herbicide – apply
treatments to roadsides after
rainfall when the leaves are
What is triclopyr?
Triclopyr is a selective herbicide for broadleaf plants (it does not kill
monocots such as grasses and bulbs). Product names include Garlon,
Access, Ranger, Triclon, Viroaxe, Timbrel. This chemical imitates a
plant hormone that causes the growing tips to elongate, followed by
distortion, withering and death of the plant (Cox 2000). Grasses survive
because they are able to transform triclopyr into compounds that do
not have hormonal activity. Triclopyr can be acutely toxic to humans
with symptoms including lethargy, in coordination, weakness, difficult
breathing, tremors and diarrhoea. It is corrosive to eyes with damage
lasting for three weeks and is a skin irritant. Laboratory tests on dogs
and rats result in the development of kidney problems. It also known
to slow down frogs, inhibits the growth of mycorrhizal fungi, inhibits
nitrogen cycling, and damages mosses and lichens. The chemical can
last in the soil for about 100 days, but reports of persistence for more
than a year are also present. The chemical is mobile in the soil, so is
easily washed into rivers and even ground water. Contamination of
urban streams with tricolpyr may be widespread in the USA (Cox 2000).
The breakdown product of triclopyr is TCP. TCP in concentrations
of only 0.2 ppm disrupt growth in human foetuses. TCP is also very
mobile in the soil and is toxic to soil bacteria. However, other sources
of information such as Dow AgroSciences indicate that there should
not be a problem with the use of this herbicide. Conflicting reports on
the impacts of tricolpyr should be regarded as a warning sign that a
lot is still to be learnt about the impacts of tricolpyr on humanity and
the environment. We need to be aware that there are unknown risks
associated with using these herbicides and their formulations.
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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