Visualizing Environmental Science

Controlling Agricultural Pests 367

!LTERNATIVEMETHODSOFCONTROLLINGAGRICULTURALPESTS sTable 14.1

Pest control method How it works Disadvantages

Cultivation methods Interplanting mixes different plants, as by

alternating rows; strip cutting alternates crop

harvest by portion—remaining portions protect

natural predators and parasites of pests

No appreciable disadvantages; more care must be

taken in harvest

Biological controls Naturally occurring predators, parasites, or

disease organisms are used to reduce pest

populations

Organism introduced for biological control can

unexpectedly affect the environment or other

organisms

Pheromones and hormones Sexual attractants (pheromones) lure pest

species to traps; synthetic regulatory chemicals

(hormones) disrupt pests’ growth and

development

Hormones might affect beneficial species

Reproductive controls Sterilizing some members of pest population

reduces population size

Expensive; must be carried out continually

Genetic controls Selective breeding or genetic engineering

develops pest-resistant crops

Plant pathogens evolve rapidly, adapting to

disease-resistant host plant; plant breeders forced

to constantly develop new strains

Quarantine Governments restrict importation of foreign

pests, diseases

Not foolproof; pests are accidentally introduced

Irradiating foods Harvested foods are exposed to ionizing

radiation that kills potentially harmful

microorganisms

Consumers concerned about potential radio-

activity; irradiation forms traces of potentially

carcinogenic chemicals (free radicals)

allows farmers to control pests with a minimum of envi-

ronmental disturbance and often at minimal cost. IPM

is based on two fundamental premises. First, pests are

managed rather than eradicated. Farmers who adopt IPM

allow a low level of pests in their fields and accept a cer-

tain amount of economic damage from the pests. They

periodically sample the pest population in the field to

determine when the benefit of using pesticides exceeds

the cost of that action. Second, IPM requires that farm-

ers be educated to understand what strategies will work

best in their particular situations. To be effective, IPM

requires a thorough knowledge of the life cycles and

feeding habits of the pests as well as all their interactions

with their hosts and other organisms.

1. What is a broad-spectrum pesticide?


2. What are two important benefits of pesticide
   use?


3. Discuss two problems associated with the use
   of pesticides.


4. How can pests be controlled without pesticides?

Tools of Integrated Pest Management (IPM)
Uʈ}ÕÀiÊ£{°£n

IPM

tools

Resistant

crop

varieties

Natural

enemies

Pheromone

traps

(use pheromones

as lures)

Judicious

use of

pesticides

Cultivation

practices

(IPM; Figure 14.18). IPM is an important part of sustain-
able agriculture.
Because conventional pesticides are used sparingly
in IPM, and the least toxic pesticides are applied, IPM