TECHNICAL PAPER # 65
H. C. Cox
1600 Wilson Boulevard, Suite 500
Arlington, Virginia 22209 USA
703/276-1800 . Fax: 703/243-1865
Understanding Integrated Pest Management
[C]1989, Volunteers in Technical Assistance
This paper-is one of a series published by Volunteers in
Assistance to provide an introduction to specific
technologies of intrest to people in developing countries.
The papers are intended to be used as guidelines to help
people chooe technologies that are suitable to their
They are not intended to provide construction or
details. People are
urged to contact VITA or a similar organization
for further information and technical assistance if they
find that a particular technology seems to meet their needs.
The papers in the series were written, reviewed, and
almost entirely by VITA Volunteer technical experts on a
Some 500 volunteers were involved in the production
of the first 100 titles issued, contributing approximately
5,000 hours of their time.
VITA staff included Patrice Matthews
handling typesetting and layout, and Margaret Crouch as
The author of this paper, David Pimentel is a professor of
at Cornell University in Ithaca, New York.
It was reviewed
by H.C. Cox, a consultant in agriculture, Michael Dover,
an environmental consultant, Jon Myer, an engineer at the
Research Laboratories, Ron Stanley, who is employed by the
Environment Protection Agency in agricultural development,
Allen Steinhauer, the Executive Director of Consortium for
VITA is a private, nonprofit organization that supports
working on technical problems in developing countries.
offers information and assistance aimed at helping
and groups to select and implement technologies appropriate
VITA maintains an international Inquiry Service,
a specialized documentation center, and a computerized
roster of volunteer technical consultants; manages long-term
field proejcts; and published a variety of technical manuals
UNDERSTANDING INTEGRATED PEST MANAGEMENT
VITA Volunteer David Pimentel
When the new synthetic pesticides were first used on world
in 1945, some people believed that the `magic bullet' or
specific weapon for pest control had been discovered.
As a result,
ecological studies of pests--their life histories and
environment--declined and investigations of nonchemical
were drastically reduced.
In the industrialized countries, pesticides
were the main method of pest control for nearly three
With pests destroying about one-third of all crops in the
and the significant damage occurring in developing countries
[Reference 1), it is no wonder that many farmers felt
enough to consider that pesticides were the only
for a short time, there was widespread hope that losses
to pests could significantly be reduced by the use of
In fact, heavy pesticide use did result in major reductions
the damages by some pests for short periods, but no overall
reduction in losses from pests has occurred.
For example, since
1945, U.S. crop losses to pathogens and weeds have
have not declined.
Changes in Agriculture
Rather, surprisingly, U.S. crop losses due to insects have
doubled (from 7 percent to about 13 percent) .
This has occurred
in spite of a more than 10-fold increase in the use of
Fortunately, in recent decades,
the impact of this loss has been offset effectively by
crop yields. The
increase has resulted from planting higher-yielding
varieties and using more fertilizers, other fossil-energy
inputs, and irrigation.
Similar changes in crop-growing
practices occurred throughout the world.
The significant increase in insect damage to U.S. crops can
accounted for by some of the major changes in agricultural
since the 1940s.
These include the planting of crop varieties
that are susceptible to insect pests; destruction by
of such natural enemies of pests as beneficial insects
and mites; and increased use of fertilizers.
In the United States
as elsewhere, all of these changes required additional
treatments, for example in cotton, and led to the
pests resistant to pesticides.
Moreover, reducing crop rotation
and crop diversity and increasing the use of single crop
(monoculture) resulted in the need for more insecticide
use, for example in maize.
Concurrently, the U.S. government
reduced tolerance levels for insects and insect parts in
foods, and processors and retailers raised `cosmetic
for more perfect fruits and vegetables.
Farmers removed less crop debris from their fields and
often to achieve the benefits of reduced water evaporation
However, the practice also often led to increased
pest problems. For
example, less attention is now given to the
destruction of infected fruit and crop residues (e.g.,
Reduced tillage, with more debris left on the land surface,
The culturing of such crops as potatoes and broccoli has
extended into new climatic regions and made them more
to insect attack. In
addition, the use of pesticides that alter
the physiology of crop plants has made some crops (maize,
example) more susceptible to insect attack.
Costs of Pesticide Use
Pesticides have helped to control some posts.
heavy use has brought serious social consequences and
changes in the environment.
Human poisonings by pesticides are
the highest price paid for intensive pesticide use.
Each year in
the world, an estimated 500,000 humans are poisoned by
with 10,000 fatalities.
Another indirect cost of pesticides is the reduction in the
numbers of natural enemies of pests.
When this occurs, more
pesticide must be used to control the resulting pest
With cotton, for example, four to five additional sprays are
applied to compensate for the destruction of natural enemies
the cotton bollworm and budworm.
Annually, the cost of these
added sprays needed to offset the loss of natural enemies on
crops amounts to an estimated US $153 million.
High pesticide use often results in pests that develop
to the chemicals. To
cope with this, growers apply higher doses,
additional sprays, and more powerful pesticides.
annual cost of coping with increased pest resistance to
for U.S. crops is about $134 million and for the world,
$600 million. Yet,
increased pesticide use encourages further
resistance and amplifies environmental problems associated
their use. Other
harmful effects of pesticides include the destruction
of honey bees, reduced pollination, fish kills, and the
unintentional killing of crops (herbicides, etc.). Overall,
environmental and social costs annually total at least $1
Given this background to the problems associated with the
factor' approach to pest control with pesticides, several
suggested the need for an approach that considered many
environmental factors, even if their consideration led to
just one factor in the environment.
Studies of apple-pest
control in Canada in the early 1960s and of malaria-carrying
mosquitoes in the Tennessee Valley (USA) in the 1930s were
forerunners of integrated pest management, confirming the
for an interdisciplinary systems approach to pest
was an approach that took into account the interactions
pest species and with plant hosts, as well as the life
and environments of both.
(Nonchemical controls had, of course,
been used with and without chemicals for many years.
integrated pest management (IPM) has grown and has now
stated goal of most pest control operations in most
This paper examines the complex nature of pest problems and
evaluates both chemical and nonchemical controls.
of IPM are assessed, together with its current
and its future as a pest-control strategy.
Although the paper
emphasizes agriculture, the concepts and strategies of IPM
also be applied to forestry, the management of range and
land, the control of insects that carry human and animal
and the control of such urban pests as rats and cockroaches.
The agricultural uses of IPM vary greatly with local
In addition to the general concepts in this paper, specific
information is available in most countries from
agricultural centers and government research stations.
STRATEGIES OF INTEGRATED PEST MANAGEMENT
Integrated pest management is a technology for controlling
and other pests for the benefit of society as a whole.
In agriculture, pest-control strategies must consider not
the pest in its total agricultural environment, but also the
surrounding environment and society that agriculture serves.
In developing strategies for an IPM program, reliable
on the following is vital:
1. The ecological
basis of the pest problem.
2. Factors in the
agroecosystem that can be manipulated to make
environment unfavorable for weeds, insects, and
while producing an optimal crop yield.
3. A target level
for reducing the post population, below
which the degree
of damage is acceptable.
4. Pest and natural
enemy population trends, based on careful
determine if and when pesticide treatments are
5. An analysis of
the benefits and risks of the proposed IPM
the farmer and society as a whole.
Knowledge of the ecological basis of the pest problem,
in depth later, suggests ways to alter the crop environment
reduce pest problems and losses.
Some nonchemical environmental
manipulations to control pests will also be discussed.
IPM is a first line of defense.
Not all pest problems, however,
can be solved by manipulating factors in the crop
Thus, the second line of defense is the use of
a pesticide is needed, it should be used, but in such a way
cause minimal damage to the natural enemies that also are
controls of the major and potential pests.
extensive knowledge of the ecology of the pest as well as
beneficial natural enemy populations.
With adequate information
on beneficial and pest populations, a pest-control
determine which pesticide to use and when to apply it for
The decision of when a pesticide should be applied will also
depend on the level of injury by the particular pest at
there is a significant economic loss.
injury levels' requires detailed knowledge of the following:
1. Density of a
2. Densities of its
parasites and predators.
3. Temperature and
moisture levels and their impact on the crop,
pest, and the
pest's natural enemies.
4. Level of soil
nutrients available to the crop.
5. The growth
characteristics of the particular crop
6. Crop(s) grown on
the land the previous year.
Of course, using a combination of nonchemical controls plus
keeping pesticide applications to a minimum has
and public health advantages while at the same time being
to the farmer. First
of all, reducing pesticide use reduces
crop production costs.
Second, and equally important, using a
combination of controls including pesticides reduces the
of the pests being able to overcome all of the control
This relates especially to overcoming the resistance to
the pest that the host plant has (`host-plant resistance')
develop As a result,
the useful life of both nonchemical and
pesticidal controls and their benefit to society could be
Another important reason for using several control methods
is that the climatic and other environmental factors change
and may render one or more control factors less effective
Although nonchemical controls offer fewer risks to the
than do pesticides, they are not without risks.
and perhaps the most important step in developing successful
strategies entails a careful benefit and risk analysis of
technique, including measuring its environmental and social
costs. This is
essential if the control program is to provide
maximum benefits to agriculture and society as a whole.
IPM is a highly complex technology, even if the complex
of pest groups in an agroecosystem is understood (see
Furthermore, manipulating the numerous factors in an
agroecosystem to make the environment of a pest unfavorable
maintaining a favorable environment for the crop is a major
Selecting' and balancing nonchemical controls and
pesticides to use in combination is a difficult task.
can be aided by carefully analyzing the benefits and risks
an IPM program, taking environmental and other biological
into consideration as described above.
Although IPM has a complex basis, it sometimes uses only one
control technique; for example, in some situations well
and managed crop rotation can reduce the level of a pest
to tolerable levels, and keep it there, without the use of
other types of control methods.
NONCHEMICAL PEST CONTROLS
IPM uses combinations of nonchemical pest controls including
biological controls, host-plant resistance, cultural, and
techniques. The term
"nonchemical control" refers to human activities
that manipulate the pest's environment, its ecological
relationships, or a combination of these [5, 6].
Again, it must
be emphasized that there are no instant, magical control
whether they are pesticides or nonchemical controls.
populations must be managed in the context of the total
Resistance of Host Plants
Many plants in nature have evolved to limit the feeding of
on them. Through
careful selection and breeding, genes can be
incorporated into a cultivated plant that confer resistance
specific pests and thus provide effective control.
the Hessian fly, a serious pest of wheat, is effectively
on a large portion of U.S. wheat cropland because the wheat
is bred for resistance to the fly.
Similarly, the spotted alfalfa aphid in controlled on most
the U.S. alfalfa crop by host-plant resistance.
the pea aphid has also been bred into some alfalfa varieties
is helping to control this pest.
To date, the most successful use of host-plant resistance
been in the control of plant pathogens.
Breeding for disease
resistance is a widely used control strategy, and now most
crop varieties have been developed to incorporate varying
of resistance to one or more important diseases.
For some crops,
like small grains, up to 98 percent of the world total is
to resistant varieties.
In selecting and breeding plants for host-plant resistance
pests, the nutrients or the level of chemical toxicants in
new variety may be altered and the plant's resistance to
For example, some standard maize varieties
with high levels of carotene (vitamin A) have been found to
more resistant to maize leaf aphids than lines with lower
However, high levels of vitamin A can be harmful to
animals and humans, and such changes need not be beneficial
humans and livestock using the maize.
In addition to variations in nutrient levels that often
levels of pest populations, many plants produce chemical
that diminish or prevent pest attack.
For example, the potato
plant produces them in leaves, stems, and sometimes even in
tuber. At certain
dosages these are toxic to some pests; unfortunately,
for potatoes that have turned green from being left in
sunlight, they can also poison humans.
Parasites and Predators for Biological Control
The deliberate use of predators and parasites, including
to control several insect pests has proved to be
The first effort to employ predators and
parasites for biological control occurred late in the 19th
when the Australian Vedalia beetle was brought to California
to control the cottony-cushion scale on citrus [7).
this technique has been used extensively on more than a
hectares of crops including citrus and olive .
biological control in being achieved on other crops like
alfalfa, and maize .
Possibly the most successful biological
control project to date is the importation from Argentina of
wasp that (dropped from aircraft in Africa) parasitizes the
This project has reduced cassava losses from 80
percent to 40 percent of the crop; the crop losses since
estimated at $5.5 billion.
In addition to controlling insects, predators and parasites
control plant pathogens.
Recent research at the USDA Beltsville
laboratory has demonstrated that one species of fungus
a different one that causes 'leaf spot' in lettuce and
more than 200 other food crops.
Great potential exists for the
expanded use of biological control measures against plant
Insects and microorganisms are also used to control weeds
One of the most successful examples of this was the
of two species of leaf-feeding beetles to control the
weed pest in California.
As a result, the weed has been controlled
effectively on more than 1.5 million hectares of cropland,
both in California and neighboring states.
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Great care must be exercised in using plant-feeding insects
plant pathogens for weed control, because they may pose a
to crop and natural plants in the total system.
No major problems
have resulted in modern times from the introduction of
biological controls for weeds.
Indeed, the existing levels of
risk are very low because of the ways that research is
and its results made available to farmers.
Crop Rotation and Multiple Cropping
Rotation of crops is a most useful technique for controlling
pest insects, diseases, and weeds.
The adverse effect on pest
outbreaks of continuous culture of the same crop on the same
has been discussed.
Therefore, it is not unexpected to find that
rotation of crops such as susceptible maize, in an
sequence with other crops, results in effective control of
maize rootworm complex.
Multiple cropping and intercropping can
reduce pest populations and the damage they inflict.
Although many crop rotation programs help to control some
inappropriate rotation of crops may cause other
example of this is planting potatoes after a crop of pasture
grasses, which may result in serious wireworm problems.
emphasizes the need to take into account the total system
managing crope and pests.
Timing of Planting
Some pests can be controlled, or their injury reduced, by
the crop when the pest is not present.
In this way, the most
susceptible stage of crop development does not coincide with
peak of the pest population.
This strategy is used for controlling
the Hossian fly: large areas of wheat are planted well after
the Hessian fly has emerged and when a large percentage of
population has died for lack of suitable host plants.
has also proved to be effective in reducing the damage
from root and crown rot in winter wheat and winter barley.
The prime risk is in exposing the newly planted crop to
pest that may emerge at the new planting time.
Other risks of
altered planting times include exposing the crop to drought
rainfall in less during the later cropping schedule, to
planted too early, or to immaturity at harvest if planted
The technique of releasing insects that have been sterilized
gamma radiation or by chemical sterilants, to compete with
insects for mates, has been highly successful with the
fly. Release of sterile
screwworm males destroyed the reproductive
capacity of the screwworm fly population and eradicated the
pest from the United States and parts of Mexico.
In some parts
of California, it has been successful against the
fruit fly. Although the
goal in these cases was eradication, the
sterile-male technique is of potential value in IPM.
technique is not successful against all kinds of insect
and some pest populations may become "resistant"
to it. Other
genetic technologies such as introducing lethal genes and
male-producing genes also offer potential for insect-pest
There is a chance of releasing a new genotype that will
greater risk than those already present.
In addition, if some
pests are not completely sterile when released, they may
and contribute to the pest problem.
The risks are acceptably
small under today's conditions of agricultural research.
The enhancement or curtailment of water supply to crops
the ecosystem and in this way sometimes helps to control
pests, plant diseases, and weeds.
For instance, irrigation of
alfalfa fields has been reported to encourage vigorous
attacks on the spotted alfalfa aphid and pea aphid
Limiting the application of irrigation water to only the
area of a plant and avoiding wetting the leaves and fruit
reduce certain disease outbreaks in apple and citrus
flooding of rice fields has been managed to suppress certain
Unsuitable water applications to crops can encourage plant
outbreaks such an scab on apple trees and mildew on cucurbit
Simple techniques such an tilling the soil often help to
certain pests. For
example, U.S. wireworm populations,
have a two-year life cycle, can be reduced by plowing the
during the summer.
Mechanical injury, exposure to summer heat,
bird predation, and low humidities probably account for most
the mortality in the wireworm populations.
Turning over the soil buries most plant pathogens present on
surface, thereby reducing the chance for future crop
. Worldwide, soil
manipulation is the primary means of weed
control. Young weeds
are uprooted, buried, or disturbed, resulting
in a high mortality in weed populations, especially when
conditions are dry.
Tilling the soil destroys some pests effectively; however,
the same time, tillage exposes the soil to wind and water
Soil erosion has become a major environmental problem in
the world and primarily is due to use of the plow for weed
The risks and benefits of this strategy must be evaluated.
Minimum tillage offers a different set of benefits and
For years, agriculturalists have known that field sanitation
an effective way to control insects, plant diseases, and
Plowing-under crop residues has, for a long time, proved to
effective technique for controlling various pests that
might over winter for the next growing season.
Many weeds drop
their seeds on the soil surface, and some species will not
when plowed under.
But some weed seeds may survive for
many years in the soil.
Any technology that is employed to eliminate
sources of pest infestation will reduce the chances of pest
Destroying weeds and other vegetation close to crops to
clean culture, however, may not always be beneficial.
leafhopper and its parasite are normally maintained at low
on the blackberry growing in vineyard borders.
When the leafhopper
invades the grapes, the readily available parasites on
the blackberry invade the vineyard at the same time and
control of the leafhopper.
As a result, leaving wild blackberry
to grow adjacent to grape vineyards has helped to maintain a
parasite population that has provided the prime means of
of the grape leafhopper.
Planting appropriate combinations of crops together may help
reduce the pressure of major peats on each crop .
in central America, combinations of maize and beans grown
have had fewer pest problems than either crop grown by
itself. So far, this
technology has not been used extensively in
other locations, but it deserves greater attention.
Although the combination planting of certain crops has
it may also result in more serious post outbreaks than if
each crop were grown as a monoculture.
For example, growing maize
in association with either cotton or tobacco is more likely
increase some pest-insect populations than if the crops were
produced as monocultures.
The ecology of each crop must be
clearly understood before combinations are used.
To a limited extent, cardboard, plastic, and other types of
physical barriers have been used to control insects and
Thus, wrapping the stems of trees and shrubs with paper tape
prevent insect borers from attacking them.
The most widespread and successful use of barriers has been
weed control, where organic and black plastic mulches have
to be highly effective.
However, this technique is costly in
both labor and materials and is generally used with
crops such as market-garden vegetables.
Although organic mulches are effective in controlling weeds,
they may encourage other pests such as slugs and mice.
organic mulches may also reduce soil temperatures and thus
germination and rate of growth of certain crops; plastic
can increase water runoff from the crop fields and cause
of other land.
Destruction of valuable crops by plant pathogens can be
by planting only disease-free propagated material and
eliminating the source of any plant pathogens.
In the United
States this practice is widespread, especially in fruit
Now, nearly all fruit trees are certified disease-free
Fortunately, no known risks are associated with this
control technology when practiced as described above.
INTEGRATED PEST MANAGEMENT AND THE FUTURE
For the farmer, the main advantage of IPM is reducing the
of pesticide, that in used.
This reduces the cost of pest control
while protecting the environment and public health.
A weakness of IPM in the need for research to establish the
technologies, which are more complex and sophisticated than
routine spraying. In
addition, educating farmers in the use of
IPM technologies is more difficult than training then to
crops once a week or once in two weeks.
What are the immediate prospects for IPM in developing
They are good in those situations where farmers can be
to monitor the pests in their crops and "treat only
Local agricultural research and extension officials and
farmers often have a sense of the "economic-injury
level" and can
thus develop an initial IPM program for "treating when
For the long term, devising pest-control strategies with the
necessary degree of sophistication will require the joint
of such specialists as entomologists, plant pathologists,
specialists, agronomists, plant breeders, and
1. Davies, J.C.,
"Integrated Approaches to Pest Management:
of Food." In Shemilt, L.W. (ed.), Chemistry
and World Food
Supplies: The New Frontiers, CHEMRAWN II, pp
U.K.): Pergamon Press, 1983.
2. Huffaker, C.B.
ed., New Technology of Pest Control. New York:
John Wiley, 1980
3. Kennedy, Donald
(Chmn.), Pest Control: An Assessment of
Alternative Technologies, vols. I-V. Washington,
Academy of Sciences, 1975 USA.
4. Oka, I. N.
"The Potential for the Integration of Plant Resistance,
Biological, Physical/Mechanical Techniques,
for Pest Control in Farming Systems." In
(ed.), Chemistry and World Supplies: The
CHEMRAWN II, pp 173-184. Oxford (U.K. : Pergamon
5. Pimentel, D.
(ed.), CRC Handbook of Pest Management in Agriculture,
Vols. I-III. CRC
Handbook Series in Agriculture.
Florida: CRC Press, 1981 USA.
6. Pimentel, D.,
"Agroecology and Economics." In Kogan, M.
(ed.), Ecological Theory and Integrated Pest
299-319. New York: John Wiley and Sons, 1986
the Quality of Our Environment," Report of the
Pollution Panel, President's Science Advisory
Washington, D.C.: The White House, 1965 USA.
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