Integration of Biological and Chemical Control
Introduction
1
and Principles
By RAY F. SMITH, Professor of Entomology
Department of Entomology and Parasitology, University of California, Berkeley
Native biological control agents are often important regardless of whether or not man deliberately introduces,
manipulates or modifies them.
Integrated control is based on the use of fundamental
ecological principles to control and manipulate pest insects and mites. It has as a prime goal the combination
and integration of biological and chemical control. The
integrated control programs which have been developed
to date emphasize the utilization of both chemical and
biological measures because these two techniques are our
main standbys in the struggle against insect and mite
pests. In the final analysis, however, we must integrate
not only chemical and biological control but all control
procedures and techniques into a single pattern aimed at
profitable production.
In this introduction, I would now like to restate what I
consider to I:e three basic principles of integrated control.
Tlte First Principle emphasizes the ecosystem concept
and may be stated as follows: The complete complex of
organisms, the culture of the crop and the conditioning
environment
are considered together as a unit-the
ecosystem.
This ecosystem includes all the pest insects and mites,
the plant diseases, the natural enemies of the pests, their
competitors, the plant and its culture, the weeds, the
soil and its management, the conditioning environment and
in some cases other aspects. Eight years ago in an address
at the Entomological Society of America meetings in
Los Angeles, Robert Glen clearly indicated the fundamental role of be ecosystem in determining insect abundance.
His address was later published in Volume 47 of the
JOURNALOF ECONOMICENTOMOLOGYand should be required reading for all students of entomology. Suffice it
for here, the important interactions of the agricultural
ecosystem must be understood thoroughly if we are
to manage pest populations successfully.
It is my opinion that the integrated control approach
to pest problems is a necessity in modern agriculture. If
we are to maintain over the years profitable production of
high-quality, wholesome agricultural programs, some of
our current pest control procedures must be modified. It
is for this reason that we as entomologists, knowing the
real and potential impact of insects on man's economy,
should take a careful look at the possibilities of integrated
control.
Statements calling for changes in pest control have
been originating with increasing vigor in recent years
from wildlife conservationists, organic farmers and some
public health representatives.
My statement, however,
originates from a different viewpoint-that
of practical
agricultural
pro~uction.
Pest control programs, based
largely on chemicals, have produced various unwanted
side effects and have continually run into difficulties.
This evidence is forcing economic entomologists to take
a fresh look at the modern research attack on pest problems .. At the same time, every forward-looking
agricultUrist (farmer, researcher or agribusinessman)
should
realize the dilemma that the agriculture industry is facing
in the area of pest control and should seek or demand
a solution.
Tlte Seco'ld Principle stresses economic levels and may
be stated as follows: The population levels at which the
pest species causes harm, damage or is a nuisance must
be determined and control measures directed to keep pests
below these economic levels rather than to attempt to
eliminate tl:em completely.
Integrated control is a relatively new name for a philosophy of pest control which some, but unfortunately not
all, econo~ic .entomolog!sts have been using for many
years. It IS simply apphed pest control which combines
and integrates biological and chemical measures into a
single unified pest control program. Chemical control is
used only where and when necessary and in a manner
which is least disruptive to beneficial regulating factors
of the environment. Integrated control may make use of
naturally occurring parasites, predators or pathogens as
well as those biotic agents which are artificially increased
or introduced.
It should be clear that I am using the term biological
control in a very broad sense. I include any action of
parasites, predators or pathogens which lowers the general
level of abundance of an organism. The organism need
not be of economic importance or if it is of significance
to man the action need not result in economic control.
Very low economic levels as occur in some situations
make satisfactory control very difficult in any case but
low economic levels create special difficulties especially
so for biological control and integrated control. The
higher the economic level, the greater will be the possibility that biological control agents can come into play
and hence the greater the opportunity for integrated
control.
This second principle, which has also been called
the "dirty field technique," will be difficult for most
modern farmers to comprehend. Growers have been conditioned to want beautiful, clean, insect-free plants in
their orchards and fields. They must now be reconditioned
to tolerate pest populations at sub-economic levels and to
refrain from attempts at eradication through chemical
control.
Tlte Third Principle underlines the importance of
avoiding d:sruptive actions. It may be stated as follows:
Necessary control measures should be designed to give
adequate control but in a manner which does not upset
some other part of the ecosystem.
1 Presented in ~ joint symp?sium of subsection C·a, Biological
Control, and sectIon F, Chemical Control at the annual meeting
of the Entomological Society of America in Miami, Florida, November 27·30, 1961.
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This third principle involves the application of the first
two princi:;>les and the selective use of insecticides, aug~entation of natural enemies, and in some cases superVised control. In other words, maximum chemical augmentation of the biological control of a given pest with the
least disruptive affect by these chemicals on the ecosys-
By completely effective, I mean that they keep the potential pests below the economic threshold all or nearly
all of the time. The fact that we have numerous economic
insect pests is in itself some evidence that the biological
control agents that we do possess are not perfect.
tern to which the pests belong. The exact manner in
which this can be achieved will, of course, vary from
crop to crop and area to area.
All this discussion of integrated control presupposes
the presence of biological agents which are at least partially effective. If they are not present, we have nothing
to integrate. It is of little value to know that a particular
pest has a natural enemy. We must know its importance
and significance in the population regulation of the pest
species and perhaps other potential pests. Some natural
enemies are of little or no significance in population determination and are in fact merely dependent on the host
as a source of food. There is no great practical value in
protecting or fostering such natural enemies just because
they happen to be parasites or predators. Other natural
enemies are partially effective, that is, they are important in reducing the pest populations to subeconomic levels
in some years, in some places, or in certain seasons, or
they contribute to a lower general level abundance.
Such partially effective natural enemies are very important in integrated control programs. It is the aim of integrated control to augment such partially effective
natural enemies and to supplement their effectiveness with
chemical controls when they are temporarily ineffective.
Although it is probably impossible to determine accurately,
I would guess that there are more partially effective
natural enemies than there are completely effective ones.
The many problems associated with the use of pesticides are known to us all. The development of tolerance
to pesticides, secondary pest outbreaks, rapid Harebacks
of treated pests, destruction of pollinators, excessive spray
residues, hazards to wildlife and other related problems
seem to plague us on every hand. However, the positive
values that can accrue from the use of chemicals should
not be forgotten, and they should stimulate us to develop
means of overcoming these difficulties. Chemicals are
essential to our agricultural economy and we must seek
out every possible solution to overcome whatever shortcomings they may have. It is my opinion that at least
in certain situations, integrated control can be one such
solution.
It is a practical and effective approach to the solution
of some of our most serious pest problems. It has limitations and cannot be applied immediately or universally.
Nevertheless, with careful research and cooperation of
all concerned it can be put into practice. It holds much
promise and should be a prime guideline in much of our
applied investigations.
Integration of Biological and Chemical Control
Desirable Attributes oj Biotic Agents
By BRYAN P. BEIRNE, Director
Entomology Research Institute for Biological Control
Canada Department of Agriculture, Belleville, Ontario
From our viewpoint, biotic and chemical control agents
have one desirable attribute in common: they kill harmful insects. In the ways they do this and in what else
they do each has both desirable and undesirable attributes.
Thus, one of these kinds of agents used alone will not
normally give optimum control: it will not provide the
best combination of efficiency in destroying noxious insects with ease and economy of application and the
minimum of harmful side-effects.
result in accumulation of residues harmful to plants, animals, or man whereas the insecticide residue problem is
becoming increasingly serious. And, so far as present information indicates, pest resistance to biotic agents develops much less frequently, readily and rapidly than resistance to chemical control agents.
There are three main approaches to the application of
biological control. Each exploits particular desirable attributes of the agents used. In one approach new enemies
of pest species are introduced and established; in another
the environment is manipulated to foster already-present
enemies. The primary reasons for using both of these approaches are the attributes of self-perpetuating permanent
control and of pest-seeking by the biotic agents. The first
approach has been applied against many pests in many
countries and is what is commonly thought of as biological
control; the second is receiving special attention in the
Soviet Union and increasing attention in North America.
In the third approach the biotic agents, usually microbial
pathogens, are applied in the same manner as chemical
insecticides, and for the same purpose, namely, to obtain
rapid and effective, though usually only local and shortterm, control. Here the main reason is to avoid the undesirable results of using chemical agents. Though this
approach is being given rapidly-increasing
attention, and
much work has been done on it in recent years, its full
potentialities
are still largely undeveloped for most
practical purposes.
Biotic agents have a major positive advantage over
chemical agents: they are living organisms and thus
can seek, find, and attack the pests, and can be selfperpetuating and can multiply and spread. A successful
biological control attempt by introducing new agents into
an area results in a permanent lowering of the average
level of a pest population there, and eventually in neighboring areas, without further human intervention. Existing chemical controls cannot do this; they lower the
pest population only on a local basis and only temporarily,
or temporarily prevent it from increasing, but to keep it
down they must be reapplied regularly with consequent
trouble and expense.
Other main desirable attributes of biotic agents are
primarily the absence of the main undesirable attributes of
chemical agents. Chemical agents affect most insects with
which they come in contact, including beneficial organisms,
and this often creates new pest problems, but biotic agents
are for all practical purposes specific to the insects against
which they are applied. Use of biotic agents does not
To use biological control alone because of the desira-
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