BIO-CONTROL
Natural methods
cause less
damage
S
mallholders who favour
methods of planting that
are environmentally
friendly and as natural as
possible will probably have
encountered commercially
available products that are
described as “biological
control” products.
The Gauteng Smallholder has
written in the past of the use
of biological control in
combating invasive alien
plants. This entails bringing
natural enemies of alien
plants from their native
countries and introducing
them into habitats where the
plants are threatening local
vegetation. These enemies
may be insects, bacteria or
fungi.
However, there are pest and
disease control products
available that work on the
same principle, offering a
method of controlling pests
and diseases using their
naturally-occurring enemies
or biological antagonists.
These living organisms may
be predators (predatory
mites, ladybirds etc),
parasitoids (wasps etc) or
microbes (fungi, bacteria or
viruses). Biological control is
designed to reduce plant
pathogens and limit pests
such as insects, parasitic
nematodes and weeds. There
are also products that
stimulate the optimum soil
conditions.
Promoters of these wares
argue that the products are
completely natural, environmentally friendly, they benefit
crop quality, they are useful
as a stand-alone solution or
as part of an Integrated Pest
Management (IPM)
programme, there are no
chemical residues or with-
holding periods, they are
non-toxic and safe for
workers and consumers and
that there is minimum effect
on non-target organisms.
The rate at which biological
control products or inoculants
are being introduced into
South Africa has increased
rapidly since the early 1990s.
Products may have single
ingredients or be blends of
severalA
materials. Some
ingredients are recognised by
the scientific and farming
communities as having the
ability to improve crop yields
and quality. The value of
others is often unknown and
should first be evaluated for
their ability to deliver upon
the manufacturer's claims.
Some of the products target
specific pests and diseases.
The ingredient has a biological origin rather than a
synthetic chemical. This
includes fungi, bacteria,
baculoviruses (which affect
insects) and plant extracts.
Other products containing
beneficial bacteria and fungi
can be added to the soil to
improve growing conditions.
These are natural organisms
that have been depleted from
the soil due to modern
farming practices and
therefore need to be
replaced. They perform a
wide range of functions
including the degradation of
organic matter, mobilisation
and fixation of nutrients and
production of bioactive
compounds, protection from
pathogens, improving soil
structure, aeration and water
holding capacity.
Yet other products are
applied to the plants, seeds or
soil to stimulate the natural
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