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Why biological control?
Weeds in Australia are rarely weeds in their home country.
This is because many plants are hosts to a variety of insects
and pathogens (fungi, bacteria etc) that attack the seeds,
leaves, stems and roots. If plants are introduced to a new
country without these natural enemies, their populations grow
unregulated and they often become weeds.
Biological control seeks to reunite weeds with the natural
enemies that regulate populations in their home country. Insects
and pathogens suitable for biological control (called biocontrol
agents) are specific to the target weed and will not thrive
on other plant species.
Bridal creeper is a native of South Africa where it is relatively
uncommon. Its populations are regulated by many natural enemies,
three of which proved safe to release in Australia. These
are: the bridal creeper leafhopper, rust fungus and leaf beetle.
None of these agents will become a pest on any other plant
species.
So why can't Australian
insects and pathogens be used as biocontrol agents?
Australian insect and pathogen species can attack exotic
plant species if they are able to defeat the plants natural
defence mechanisms (natural chemicals, leaf hardness, leaf
hairs etc). There are many exotic plant species that are attacked
by native insects and pathogens, but unfortunately some are
left unattacked and become weeds.
Will all exotic plants
become weeds?
Not necessarily. There are many exotic plants in Australia
that do not invade bushland or agricultural land. This may
be for a variety of reasons such as the absence of suitable
pollinators, inadequate environmental conditions, presence
of exotic natural enemies which were introduced with the plants
etc. However this doesn't mean these plants will never become
weeds. Many exotic plants that have naturalized in Australia
are referred to as "sleeper weeds". They are found
in bushlands where they are not yet having a great impact
on surrounding plants.
For further information on the processes involved in a biological
control program download the brochure 'Biological
Control of Weeds… The Process' (PDF
2.1MB)
Any question? Contact us
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