Biomedical Engineering Reference
In-Depth Information
slowly than direct chemical attacks and this has often restricted their use on
commercial crops. In fairness, it must be clearly stated that biotechnology per se
is not a central, or even necessary, requirement for all of biological control,
as many methods rely on whole organism predators, which, obviously, has far
more bearing on an understanding of the ecological interactions within the local
environment. However, the potential applications of biotechnology to aspects of
pest/pathogen/organism dynamics, as examined in other sections of this topic,
has a supportive role to play in the overall management regime and, thus, there
exists an environmental dimension to its general use in this context.
Biological control methods can provide an effective way to mitigate pesticide
use and thus the risk represented to the environment and to public health. In
addition, unlike most insecticides, bio-controls are often highly target-specific,
reducing the danger to other non-pest species. Against this, biological measures
typically demand much more intensive management and careful planning than
the simple application of chemical agents. Success is much more dependant on
a thorough understanding of the life-cycles of the organisms involved and can
often be much more of a long-term project. In addition, though high specificity is,
generally, a major advantage of bio-control measures, under some circumstances,
if exactly the right measure is not put in place, it may also permit certain pests to
continue their harmful activities unabated. Considering the huge preponderance
of insect species in the world, a large number of which pose a threat to crops or
other commodities and thus represent an economic concern, it is small wonder
that the global insecticide market has been estimated at over $10 billion (US) per
year. Accordingly, much of the biological control currently in practice relates to
this group of animals.
Whole organism approaches
There are three main ways in which whole-organism biological pest control may
be brought about. Classical biological control, as with the previously mentioned
Cane Toad, requires the importation of natural predators and is principally of use
when the pest in question is newly arrived in an area, often from another region
or country, having left these normal biological checks behind. Another form of
control involves conservation measures aimed at bolstering the predatory species,
which may be a valuable approach when natural enemies already exist within
the pest's range. However, the third method, augmentation, is more relevant to
the concepts of biotechnology and refers to means designed to bring about the
increase in effectiveness of natural enemies to a given pest. This may consist
simply of artificially rearing them in large numbers for timed release or may
extend to more intensive and sophisticated measures like the modification, either
by selective breeding or genetic manipulation, of the predator such that it is better
able to locate or attack the pest.
One attempt at augmentation which has been tried commercially is the
production of entomopathogenic parasitic nematodes. Juvenile stages of the
nematodes, which are then only around 500 μ m long and 20 μ m wide, can enter
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