Burning is best Sandanezwe control method
By Phila Dlamini

THE University of Swaziland together with the Ministry of Agriculture
and Co-operatives have found that burning Sandanezwe is the best
control method, especially in the farming environment.

The findings were revealed in a report on a research study to control
invasive species, specifically Chromolaena odorata, popularly known as
Sandanezwe.

The study came about following a national workshop held at the UNISWA
Faculty of Agriculture in Luyengo, where the public was sensitised on
the increasing problem of sandanezwe invasion in Swaziland. Professor
Ossom said following the successful workshop and a tour of some
Sandanezwe-infested farms in the country, UNISWA, in collaboration
with the agriculture ministry established an experiment in Bhalekane
Cattle Fattening Ranch in the Lowveld which is one of the
government-owned cattle ranches that are heavily infested by
Sandanezwe and Lantana (another alien invasive weed).

Some of the control methods investigated include: (1), slashing weeds
to the soil level; (2), digging up and exposing the weed roots and all
parts to dry up; (3), slashing weeds and, thereafter, spraying them
with a chemical called ‘Roundup’; (4), slashing weeds and
stump-spraying with a chemical called ‘Chopper’; and (5), controlled
burning of weeds. The experiment was conducted from March to July
2007, with observations (including density and type of weed re-growth
and labour requirements) made every two weeks under each control method.

“The least effective method of Sandanezwe control was slashing.

Though slashing gave an obvious, short-term and temporary control,
within a few weeks, the slashed plants sprouted, growing new branches.
Digging up and exposing weeds to dry was effective, but it was the
most labour-demanding method, requiring 9.5 man-days/hectare, compared
to: controlled burning, 5.1 man-days/ha; slashing, 5.7 man-days/ha;
Roundup, 3.1 man-days/ha; and Chopper, 2.4 man-days/ha. Of the two
chemicals investigated, Roundup gave a more effective control than
Chopper,” the report said.

It further states that though controlled burning has predictable
disadvantages (such as, if not properly controlled, the fire can
spread beyond expected limits and can also destroy some desirable
plants as well as animals in the environment), it appeared to be the
only method that could completely wipe out all Sandanezwe and Lantana
plant parts �" including any roots, stems and the ‘seed bank’ that
might be hidden underground.

Further, the report adds, “the results of this investigation are in
agreement with earlier reports on weed control experiments in other
parts of the world. Also, the manager of Mbuluzi Game Reserve found
controlled burning to be the most effective method in controlling
weeds (such as Parthenium species) and checking forest encroachment in
the game reserve.”

For small- scale farmers, it is recommended that small-scale farmers
in the Lowveld should use controlled burning to destroy Sandanezwe.
This recommendation might not be valid or effective in other
ecological zones where environmental situations might be totally
different from those in the Lowveld.

“A small-scale farmer might find it convenient to burn a small area,
or to easily dig up a few troublesome Sandanezwe plants, and he or she
may not have much knowledge about how to use chemicals. It is for this
reason that herbicide use is not recommended to the small-scale farmer
who wishes to control Sandanezwe.”

The report further adds that large-scale farmers could find the use of
Roundup more helpful and cost-effective, provided the correct
herbicide technology is properly applied. Such crucial knowledge and
skills as timing, application method, suitable conditions, herbicide
concentration, equipment calibration and herbicide costs that are
beyond the capabilities of the small-scale farmer might be purchased
or hired by the large-scale farmer.

For such a large-scale farmer who might have adequate resources to
hire or own everything that involves herbicides, it might be more
useful to apply a combination of both slashing the Sandanezwe plants
and then spraying them with Roundup.

Probably, the initial density of the weed could be among the factors
that might determine if spraying Roundup alone would suffice, or
slashing needs to be done first, followed by herbicide application.
The appropriate waiting time between slashing the weeds and herbicide
application was not investigated in this experiment, but it could
depend on a number of factors, including age and density of weeds, the
thickness of slashed vegetation covering weed stumps, prevailing
weather conditions, and other environmental and plant-related factors.

To make Sandanezwe-control recommendations that are applicable to the
whole country, long-term investigations need to be conducted in each
ecological zone.

. . . More research required

ON another note, the report adds that more research is needed in order
to find the best way to control the invasive weeds.

“The ministry of agriculture continues to monitor the Bhalekane
Sandanezwe-control experiment, with technical support from UNISWA, so
that more information on how to manage this weed in the Lowveld can be
compiled over many months or years.”

Meanwhile, the general public needs to be actively and practically
involved in the war to destroy Sandanezwe and prevent it from further
spreading.

It is crucial to kill Sandanezwe plants and prevent the yearly
formation of flowers in May/June, when thousands of Sandanezwe flowers
give rise to millions of Sandanezwe seeds that fly in the air, are
carried by rainwater, streams and rivers, or stick to livestock hair,
vehicle body parts, human skin, clothes and footwear, and Sandanezwe
seeds are, thus unknowingly moved from one place to another, where
they start new infestations.

Sandanezwe-eating goats

It is worthy to note that there is a breed of Sandanezwe-eating, Boer
goats in Swaziland. Also, there is evidence that a species of wild
animals in Mbuluzi Game Reserve also browses on Sandanezwe.

These goats and wild animals could open new avenues to research into
Sandanezwe control using biological control, without importing
foreign, biological-control organisms whose future effects are unknown
and unpredictable. Weed control using plant-eating insects was one of
the weed management methods discussed at an international conference
in Perth, Australia, in September 2007. At the same conference, a
research paper on the situation of invasive weed species in Swaziland
was also presented; attempts made to manage Sandanezwe in Swaziland
were also highlighted.

Conclusions

The following five conclusions were made from this investigation:

1. Controlled burning was the best method for controlling Sandanezwe
and other invasive species.

2. Slashing of Sandanezwe gave a short-term control, but slashed
plants eventually re-grew, resulting in more weed infestation.

3. Of the two herbicides used, Roundup was a more effective weed
control measure than Chopper.

4. Digging up Sandanezwe plants and drying them was an effective
control method, but it requires more labour than the other methods.

5. Re-establishment of both invasive species and desirable forage
species could be delayed by controlled burning, if rains did not fall
for many months.
http://www.observer.org.sz/main.php?id=40208&section=Business