This essay has a total of 318 words and 2 pages.


Give an account of the ways in which biological control can be used to control pest numbers.

The effect of predator-prey relationship in regulating populations has been exploited by
humans as a method of controlling various pests. Biological pest control is where the
natural predators (agent) of the pest ((target) are used to reduce its population to a
tolerable level. It is important to make sure that the right predator is chosen, so it
must be studied in quarantine to make sure that once the number of prey drop it will not
change to attack another species and become a pest itself. It must have a fast enough
reproductive rate in order to take control before the crop is ruined and it should be
native to the environment to avoid unforeseen effects. In general it is best to use
herbivores to get rid of weeds e.g. the use of cactoblastis larvae which makes the prickly
pear susceptible to fungi thus killing it is used in Australia. To control herbivores like
aphids, carnivores like the hoverfly are used. Parasites can control their hosts e.g. the
parasitic wasp is used to reduce the numbers of white fly larvae. In some cases such as
the screw worm fly where females can only breed once, by releasing infertile males it
makes the next generation smaller. And sex pheromones are used to tempt some species like
moths into lethal traps. Biological control is often used in greenhouses for instance by
releasing ladybirds into a confined area the number of whitefly can be reduced rapidly.

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