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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. Please refer
to <medical.htm> for 2017 update 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 underlined: 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. |