Agriculture Reference
In-Depth Information
Because each pheromone affects only one specific group of insects, their
use poses no risk of harm to other organisms, including man. Unfortunately,
only a few have been discovered and produced synthetically, and the use of
pheromones is still in the experimental stages. It is very costly to discover,
produce, and market a chemical which will be useful in controlling only one
pest species.
Juven ile Hormo nes
—Anot her type of speci es-specifi c chemi cal is
also being developed. Juvenile hormones interrupt the metamorphosis of in-
sects (and insect-like organisms). These chemicals prevent reproduction by
keeping immature insects from maturing into adults. Each chemical acts
against a single pest species and has the same advantages and disadvantages as
pheromones. The few juvenile hormones available are usually applied as a
broadcast spray to reach as many target pests as possible.
c.
Cultural Control
Cultural control methods for insects include:
•
crop rotation
•
trap crops
•
delay of planting
•
harvest timing.
Crop Rotation
—Taking infested fields out of production and leaving
them fallow or planting an alternate crop may deprive pests of host plants on
which to feed and reproduce. Rotations are most effective against insects
which have long life cycles and infest the crop during all stages of growth.
Many of the traditional rotational schemes were developed to reduce pest prob-
lems.
Trap Crops
—Other crops attractive to the pests may be planted early or
nearby to draw pests away from the main crop. Destruction of such crops at
the proper time breaks the reproductive cycle of the pest before the desired
crops are infested. To control the pickle worm in cucumbers, for example, the
grower might also plant yellow squash, to which the pest is more attracted.
The squash crop can be sprayed or destroyed before the pest can complete its
development.
Del ay of Pla nting
—Delayin g the dat e of planting may reduce the
population of certain pests by eliminating the host plant needed for food and
reproduction when the pest population is at its peak. For example, prevention
of Hessian fly damage in wheat can be avoided by delaying planting until fly
reproduction has ended for the year.
