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INTRODUCTION AND SCOPE OF BIOLOGICAL
PEST CONTROL
Dr. E. F. Legner, University
of California, Riverside (Contacts) Since 1900 the partial, substantial and complete
biological control of a large number of insects, mites, weeds and mammals has
been attained in over 70 countries.
As an adjunct to other methods, it is safe, effective and
usually permanent. Emphasis on the biological control method
can act to restore the erosion of the human environment by deemphasizing such
disruptive methods of pest control as some cultural practices, and notably
the use of broad-spectrum pesticides. California took an early lead and continues to
be one of the major centers for biological control work. By 1961, approximately 1/3d of all the
beneficial insects established in the continental United States had been
introduced by California-based organizations. --- During the 1980's and early
1990's UC Riverside and Berkeley have maintained a total of about 18
full-time professional staff plus several emeriti, and about 10 research
associates, and graduate students that vary from 10-20. On a national scale, the U. S. Department of Agriculture
employs varying numbers (25-40) of entomologists in biological control work,
depending on active programs. On the
world scene, it is estimated that there are aver 300 entomologists engaged in
classical practical biological control work.
This does not include persons engaged in fundamental research only. Economics
Some examples of individual projects give
fairly accurate figures for the damage caused by a pest of and the cost of
biological control work as follows: Permanent control of the coconut scale, Aspidiotus destructor, on the Portuguese Island of Principe off the
west coast of Africa was achieved by the introduction of the coccinellid
predator Cryptognatha nodiceps from Trinidad in
1955. Losses in copra production, the
principal crop of Principe, caused by the coconut scale were estimated at 900
tons annually, which was then worth about #72,000 (English pounds). At a cost of #200, Cryptognatha was collected and shipped to Principe by the
CIBC, which also supplied an entomologist who for one year bred the predator,
supervised its release, establishment and spread, etc. at an additional cost
of #3,500. The total cost of this
project, therefore, was about #3,700.
The financial return from the complete control has been about
#1,000,000 as of 1970, or a 1,800% return per annum. Not a bad investment! The sugar cane moth borers, Diatraea spp., have been very
successfully controlled in certain areas of the West Indies and South America
by introduced natural enemies. For
example, in Antigua the cost of liberations of Lixophaga diatraeae
during 1931 and 1945 was about #8.500.
The case return from this project in terms of increased sugar at the
factory and increased yields in the field has been about #16,000 annually
since 1934, or about 200% per annum and about #552,000 to 1961. The later acquisition of Apanteles flavipes Cameron from India further increased the
magnitude of biological control so that savings soared beyond this
level. On the island of St. Kitts,
where permanent control was achieved, the total cost of introducing Lixophaga in 1934 was
#200. The resulting benefits have
accrued to about #50,000/annum or #1,700,000 by 1970, a return of 15,000% per
annum! There are many other examples where estimates
are not so simple. Evaluation of the
worth of many of the successes listed in Chapters 23 & 24 of the DeBach
(1964) text is, unfortunately, impossible.
Chapter 1 of the DeBach (1964) shows a rough balance for biological
control work carried out in California for the interval 1923-1959. Considering a total budget outlay of about
$4,300,000 against about $115,800,000 benefits realized from just five
successful biological control projects, the citrophilous mealybug, the black
scale, the grapeleaf skeletonizer, the spotted alfalfa aphid and the Klamath
weed, it is obvious that the economic returns from funds invested have been
of the nature that any businessman would consider extremely
satisfactory. An estimate of the
present benefits being derived from these five successes are running about
$10,000,000 annually, not to mention the reduction of pesticidal threats to
the environment. It must be kept in mind that many more than
five successes are registered, but economic data is difficult to derive. However, this does indicate that
biological control, though by no means a panacea for all our pest problems,
can be a sound investment and extremely profitable venture. Important Terms Natural Enemies
(predators, parasitoids, pathogens, parasites. Organisms that prey upon other organisms, parasitize them, or
cause disease). Predators are organisms that consume more than one host
individual or prey during the course of their development. Predators are usually free-living in all
stages except the egg stage. They
kill and consume their prey either immediately or within a relatively short
period of time. Some predators feed
indiscriminately upon various developmental stages and kinds of prey; other
are more selective. Parasites are organisms that live
within the body of their hosts without killing the host, but usually
debilitating them to various degrees.
Parasitoids are insects
that reach maturity by developing upon a single host individual, eventually
killing same. Three insect orders
contain many species that have adopted the parasitoidal habit, namely
Hymenoptera, Diptera and Strepsiptera, with Hymenoptera being the largest
representative. Pathogens include viruses, bacteria, protozoa, fungi and
nematodes. They cause diseases of
arthropods. Biological Control is a
term that has been used both in a fundamental ecological sense and in the
utilitarian sense to designate a field of human endeavor. Originally, the term was defined for use
in the applied sense. Biological
control can be considered a phase of natural control or limitation. Natural
Control is the balance of nature, natural balance, population balance or
what Darwin called "the struggle for existence." Natural control has also been considered
as "The maintenance of a fluctuating population density of an organism with
certain definable upper and lower limits over a protracted period of time, by
the action of abiotic and biotic environmental factors." If we plot the density of any organism (D)
against time (T), we see that over a protracted period of time its population
density will fluctuate within certain limits and about a characteristic mean
density, that of its general
equilibrium level. Natural control is essentially permanent in the
absence of gross permanent environmental changes. It is characteristic of all plant and animal populations on the
face of the earth. Therefore,
"biological control" can be considered as representing the action of natural enemies (biotic
factors) in maintaining another organism's population density at a lower
average level than would occur in the absence. In 1919, Harry
Scott Smith <PHOTO> first
used the term biological control
to denote "the utilization of organisms for the control of population
densities of animals and plants."
Since then many definitions have been offered, generating considerable
discussion and argument. Some expand
the meaning to cover such things as breeding resistant plants and genetic
engineering. An extreme case was presented by Pollard in the
1966 Bulletin Entomological Society of America: "Parasites, predators, viruses,
bacteria, fungi, nematodes, pathogens, birds, mice, skunks, fish.....heat,
light, sound, genetics, metabolism, X-rays, laser beams, chemosterilants,
nutrition, attractants, sex lures, gamma irradiation, diapause and ecology. The simplest definition was given by the
International Biological Program:
"Using biota to control biota." Jost M. Franz of the Institut für Biologische
Schädlingsbekämpfung offered the following modification of Smith's definition
in his 1961 text: "Biological
control denotes the active manipulation of antagonistic organisms by man to
reduce pest population densities, both plant and animal, to non-economically
important levels." Autocidal Control is the
mass release of artificially sterilized or genetically inferior individuals
which are used to inundate and possibly eradicate geographically isolated
pest populations. Other Controls
include chemical, cultural, resistant varieties of crops and legislative
control (quarantine) The modern approach to pest control considers,
and in various ways utilizes, all of the eight kinds of control. As a result we have gravely suffered in
the execution of the classical approach in that only a fraction of the
control research funds has been spent on it during the past several
decades. Hopefully we are entering a
new era of awareness and will elevate the classical approach to a higher
priority, since history shows that it nest the greatest permanent effects in
pest control. Other texts and files in this
series may be viewed by CLICKING on the following: Secrets of Science <museum1.htm> History of Biological Control <museum2.htm> Introduction and Scope of Biological Control <museum3.htm> National and International Organizations Active in
Biological Control <museum4.htm> Economic Gains and Analysis of Successes in Biological
Control <museum5.htm> Trends and Future Possibilities in Biological Control <museum6.htm> Beneficial Insects
<museum7.htm> Case Histories of Salient Biological Control Projects <detailed,htm> Guide to Identifying Predatory and Parasitic Insects <NEGUIDE.1>, <NEGUIDE.2>...
etc. Insect Natural Enemy Photos <NE-2ba.PCX>, <NE-2bb.PCX>... <NE-247ba.PCX>... etc. Meal Worm Project <project.3.htm> Ladybird
Beetles <ladybird.htm> Fruit
Flies in California <fruitfly.htm> Killer
Bees <killer.htm> Monarch
& Viceroy Butterflies <31aug95.mus.htm> Everywhere
is Home <9feb98.mus.htm> Familiar
Butterflies of the United States & Canada <butterfl.htm> References: Please refer
to <biology.ref.htm>, [ Additional
references may be found at: MELVYL Library] DeBach,
P. (ed.). 1964. Biological Control of Insect Pests and
Weeds. Reinhold Publ. Co., New York. 844 p. Franz,
J.M. 1961. Biologische Schädlingsbekämpfung. Paul Parey, Berlin & Hamburg. 302 p. Nicholson,
A. J. 1933. The balance of animal populations. J. Anim. Ecol. Suppl. 2:
132-78. Pimentel,
D. 1966e. Beneficial insects.
Ecology (1966). p. 162-63. Simmonds,
F. J. 1967. The economics of biological control. J. Roy. Soc. Arts 115:
880-98. Smith, H.
S. 1919. On some phases of insect control by the biological method. J. Econ. Ent. 12: 288-92. Smith, H.
S. 1929. Multiple parasitism:
its relation to the biological control of insect pests. Bull. Ent. Res. 20: 141-49. Smith, H. S. 1935. The role of biotic factors in the
determination of population densities.
J. Econ. Ent. 28:
873-98. |