In many of the chapters of Silent Spring, author Rachel Carson ends
by speaking of methods of pest control that are alternatives to using toxic
chemicals.
One example is seen in Chapter 9 in which Carson speaks of the problem of
keeping the budworm controlled; budworm caterpillars are considered serious
pests because of the amount of damage they can do to plant life by feeding.
Instead of spraying toxic chemicals to kill budworms, Carson proposes the
method of natural parasitism, which is attributed to first
being proposed by Erasmus Darwin in 1800. Since all insects have "many natural
enemies," including microbes and other insects, E. Darwin proposed controlling
insects by using other insects to kill the pest insect.
In Chapter 17, Carson proposes using what she calls biotic
controls, which is the use of biology to solve
problems related to living organisms. In this scientific field, specialists use
their "understanding of the living organisms they seek to control" and of the
"whole fabric of life" to develop control solutions.
One method of biotic control is sterilizing male insects.
Carson states that G. A. Runner reported in 1916 the successful sterilization
of the cigarette beetle using X-rays. Lab studies in the 1920s reported
successfully sterilizing a dozen different insect species using both X-rays and
gamma rays. In 1954 Texas Department of Agriculture scientists began a field
experiment of releasing screwworms over the island of Curacao and sterilizing
them, leading to the eradication of all induced infestation. Upon success of
the field experiment, in 1957-58, a similar program was initiated to sterilize
and eradicate screwworms in the southeast of the United States since screwworms
contributed to a loss of $20 million in livestock profits each year. The
program was so successful that an animal infestation of screwworms has not been
reported since 1954. Carson also reports that since then, laboratories have
been experimenting with using chemicals rather than radiation to produce insect
sterilization. While some of the chemicals are dangerous, scientists hope that
experiments with the current dangerous chemicals will lead to the discovery of
safer chemicals to use for the same purpose.
Other studies concern the use of insects' own "venums, attractants, [and]
repellents" as insecticides (Ch. 17). For example, in the
1960s, a study was conducted using the female gypsy moth's sex attraction
chemical to draw and trick the gypsy moth into harmlessly copulating with such
things as "chips of wood, vermiculite, and other small, inanimate objects" (Ch.
17). Still other studies concern using a substance to prevent the
larvae from maturing into adulthood. And, yet another study
investigated the use of bacteria to infest insect species with disease.
As the chapter continues, Carson continues to report many alternative means,
many of which are very natural, to eliminate pest infestation.
Carson proposes an alternative approach to pest control that poses no risks to both the environment and humans. These alternatives are called "biotic controls", and are divided into three specific methods.
The first method would use chemicals found within the insects themselves to repel the insects or trap them. Instead of using a poisonous and harmful chemical, it uses the insect itself to control the pest population. This is an environmentally acceptable means of pest control.
The second method would require sterilizing male insects and introducing them into the pest population. This would gradually reduce the volume of the pest population.
The third method uses both natural bacteria and insect predators to kill off pests. Allowing insects to kill each other off does not harm the environment the way pesticides do.
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