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TRENDS & FUTURE POSSIBILITIES
In Biological Pest Control
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Stimulation to Theories in Population Dynamics and Ecology
Future of Biological Weed Control
Future of Biological Control of Medically Important Pests.
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Stimulation to
Theories in Population Dynamics and Ecology It should first
of all be pointed out that biological 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 all of our 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
(legner & Sjogren 1984. 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. Exercise 6.1-- What is the "Amount
of Effort" rule? Exercise 6.2-- What is the
future of integrated control? Exercise 6.3-- What is the
future of Insect Pathology? Exercise 6.4-- What is the
future of Biological Weed Control? Exercise 6.5-- What is the
future of Biological Control of Medically Important Pests? REFERENCES::
[Additional
references may be found at MELVYL Library ] Anonymous. 1996.). In: Bellows,
T. S., Jr. & T. W. Fisher, (eds) Handbook of Biological Control:
Principles and Applications. Academic Press, San Diego, CA. Bellows, T. S., Jr. & T. W. Fisher,
(eds) 1999. Handbook of Biological Control: Principles and Applications.
Academic Press, San Diego, CA. 1046
p. 226. Legner, E. F. 1986. Importation of
exotic natural enemies. In:
pp. 19-30, "Biological Control of Plant Pests and of Vectors of
Human and Animal Diseases." Fortschritte der Zool. Bd. 32:
341 pp. 217. Legner, E. F. & R. D. Sjogren. 1984.
Biological mosquito control furthered by advances in technology and
research. J. Amer. Mosq. Contr. Assoc. 44(4): 449-456. Mackauer, M., L. E. Ehler & J.
Roland (eds.). 1990. Critical Issues in Biological Control. VCH Publ. Co.,
New York. 330 p. |