Agriculture Reference
In-Depth Information
b.
Biological Control
Biological control of insects includes:
•
predators and parasites
•
pathogens
•
sterile males
•
pheromones
•
juvenile hormones.
Predators and Parasites—
Organisms
known to attack insect (and in-
sect-like) pests in their native environment can be imported or reared in laborato-
ries and released in infested areas. This is done only after the parasites or
predators are determined to be harmless to man, animals, plants, and other
beneficial organisms. For example, several kinds of parasites and predators of
the alfalfa weevil have been imported from Europe and Asia and released in the
infested areas in this country. Several species have become established and are
helping to reduce pest numbers. However, they do not always prevent serious
outbreaks and the resultant damage.
Patho gens
—Parasitic bacteria, virus es, and fungi may be intro duced
into an infested area to control insects by subjecting them to disease. These
disease agents, like predators, are often found in the pest's native environment.
They can be imported or they can be reared in laboratories.
For example, the use of pathogens is an important part of the pest control
program for Japanese beetles. Japanese beetles are subject to attack by two
naturally occurring species of bacteria which cause the fatal milky disease.
Preparations containing spores of the contagious bacteria are produced com-
mercially and released in infested areas.
Sterile Males
—Males of some pest insect species may be reared and
sterilized in laboratories and released in large numbers into infested areas to
mate with native females. These matings produce infertile eggs or sterile off-
spring and help reduce the pest population. This technique has been used suc-
cessfully in only a few species and is still being developed. The screw worm,
which attacks cattle, is one insect on which this technique has been effective.
Pheromones
—Some insects (and insect-like organisms) produce natural
chemicals, called pheromones, which cause responses in other insects of the
same or very closely related species. Once a particular insect pheromone is
identified and the chemical is synthetically produced, it can be used to disrupt
the behavior of that insect species. Synthetic pheromones may be used to
disrupt normal reproduction, or they may be used to attract the pests into a
trap.
