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TRENDS & FUTURE
POSSIBILITIES IN BIOLOGICAL
PEST CONTROL
Dr. E. F. Legner, University
of California, Riverside (Contacts) Biological
Pest Control tends to have its strong supporters and vehement detractors; it tends
to pass through alternate phases of popularity and loss of esteem. After 1945, biological control was, of
course, somewhat eclipsed by the over optimistic hopes generated by DDT and
other organic insecticides. We now
recognize that insecticides offer no patent solution for our entire insect
pest problems, and that indeed they generate
considerable problems. Since
the mid 1960's, certain areas have received greater research emphasis: Insect pathology and biological weed
control have developed rapidly as specialties within the field. Further research has been advanced in
developing methods of evaluating the effectiveness of natural enemies. Also there have been significant advances
in quantitative field population studies; inquiry into the extent of
naturally occurring biological and research on the augmentation and
conservation of natural enemies. Population
theories during this period actually have had relatively little impact on
biological control practice. We may
expect that much of the biological control work during the next decade will
remain similarly uninfluenced.
Biological control workers are dealing with problems of extreme
complexity. They are carrying out
field experiments involving an enormous number of unknowns. They are usually charged with solving
several pest problems concurrently, and they usually operate with limited
manpower and financial resources. Although
population dynamics has had little effect on biological control practice, it
has created a new climate of opinion with regard to biological control. Increasing importance is being attached to
biotic elements in pest control.
Biological control, like chemical control, will increasingly come to
be regarded as part of a comprehensive investigation of the total ecology of
pests. The importance of one or more key factors in regulation is borne
out by biological control, as the introduction of single species of natural
enemies lowers the average density of a pest. One
future goal for biological control will be to define the characteristics of a
natural enemy that are required to control a given pest in a given area and
to measure against these requirements the characteristics of the natural
enemies available for this purpose in nature. At present this can be done only very crudely. To accomplish this we need to catalog and
categorize the biological control potential of the various entomophagous
insects attacking economic insects and their relatives throughout the world: the task has just begun, actually. Biological
control investigations should provide a stimulating source of ideas for
studies of population dynamics and plant and animal ecology. Population dynamicists will probably
profit more in the short run from the ideas and stimulus provided by contact
with field workers, than biological control workers will benefit from
laboratory studies of the population dynamicists: much of the real good stuff is already in print 30 years or
more! Although many of the procedures
employed in biological control will largely remain empirical; that is, based
on experience derived from trial and error; as more of the groundwork of
population theory is adequately laid and is more broadly accepted, we can
expect population theory to increasingly influence biological control
practice and dictate areas requiring greater research emphasis. The future undoubtedly will also see continued emphasis on foreign
exploration and international exchange of beneficial organisms. We can expect the so-called "Amount
of Effort" rule to hold.
Increased political and financial support will be required (mixed
signs of this already beginning to show).
For example, the U. S. Department of Agriculture has been expanding in
biological control. The World Health
Organization supports biological control approaches to subdue pests of
medical importance. The National
Institutes of Health and National Science Foundation supports research on
biological control organisms Future of Integrated Control Integrated
control's future is very bright, especially with its new title
"Integrated Pest Management," that is more generally understood by
scientists and the public alike.
There is no doubt expressed concerning the importance and value of the
integrated control concept. But, much
work is left to be done in order to implement integrated control on a wider
scale. A broad interdisciplinary
approach is needed, pooling talents of research teams. This also means incorporating economic
considerations. There
are special difficulties of establishing integrated control in crops where
excessive demands for eye appeal as a measure of quality, are great. There are also great difficulties in
grower and extension personnel education.
Integrated control programs will by necessity prove to be complicated
and in some instances will require trained supervisors; and perhaps rely on
computers for decision making. Governments
can take a more active role in stimulating development of integrated control
by instituting advisory services for promoting the merits of integrated
control, supporting intensified research in ecology, systematics, population
dynamics, and in the development of selective insecticides, attractants,
repellents, etc. Governments should
take over from the chemical industry the cost of the non-paying part of
selective insecticide development.
The conclusion is that we have a long way to go before integrated
control gains widespread effective application. Future of Insect Pathology More
must be learned about the role of disease among insects, the effect of
disease on insect populations, how to accurately distinguish one disease from
another, and the nature of the pathogens themselves: the basic nature of insect diseases. More must be learned about how to control
and suppress diseases among insects beneficial to humans (e.g., in culture
and mass-rearing). Also ways must be
found to better use microorganisms to control insect pests: mass production, dissemination, and in
combination with insecticides and with entomophagous insects. The Future of Biological
Weed Control Biological
weed control's future is extremely optimistic if environmental groups
concerned with endangered species can weigh the gains and detriments
accurately. Pathogenic microorganisms
have only been used in very limited situations, but they offer excellent
possibilities, especially native pathogens to avoid the risk of
importation. The combined use of
disease organisms and insect vectors.
For example, an introduced insect might serve to transport and
inoculate a weed pathogen during its feeding or ovipositional
activities. Insects incapable of
causing adequate damage might be made more effective if artificially
inoculated with a pathogen. Since
there are more than 1,000 introduced weed species in America, and only ca. 25
weeds are presently targets for the technique, there are still relatively
unlimited opportunities for future efforts.
As new weed species invade, new programs of biological weed control
can develop. We have just begun to
understand the diversity and roles of natural enemies of aquatic weeds. Since phytophagous insects are thought to
be only secondarily and incompletely adapted to aquatic life, doubt has been
expressed regarding their application as biological control agents in aquatic
weed control. But, before any
generalizations are made, however, further evaluation of the insect faunas of
aquatic weeds is necessary. Natural
enemies other than insects show more promise, however: aquatic snails, herbivorous fish and
disease organisms. Future of Biological Control of
Medically Important Pests. Great
possibilities exist, especially where chemicals are not practical to
apply. The prospects of importation
of natural enemies has just begun to be explored. Where importation has been done, results were often
spectacular. The problem of financing
this research is great since economic losses are not neatly tied to the
problem. Local financing is
available, but rarely are there adequate funds for importing exotic
beneficial organisms. The greatest
successes are with predators and parasitoids; pathogens look excellent, but
results in a practical sense have been poor to date. 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 ] Anonymous. 1992.
Principles and Application of Biological Control. University of California Press, Berkeley,
CA. (in press). Legner, E. F. 1986.
Importation of exotic natural enemies, p. 19-30. In: J. M. Franz (ed.), Biological Control of
Plant Pests and of Vectors of Human and Animal Diseases. Fortschritte der Zool. Bd. 32: 341 p. Legner, E. F. &
R. D. Sjogren. 1985. Biological mosquito control furthered by
advances in technology and research.
J. Amer. Mosq. Contr. Assoc. (Mosq. News) 44: 449-56. Mackauer, M., L. E.
Ehler & J. Roland (eds.).
1990. Critical Issues in
Biological Control. VCH Publ. Co., New
York. 330 p. |