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TRENDS & FUTURE POSSIBILITIES
In Biological Pest
Control
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Stimulation to Theories in Population Dynamics and Ecology
Prospects for Integrated Control
Prospects for Insect Pathology
Prospects for Biological Weed Control
Prospects for 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. Prospects
for 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
remains 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. Prospects
for 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
Prospects for 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. Prospects for
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 have 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
Prospects for integrated control? Exercise 6.3-- What is the
Prospects for Insect Pathology? Exercise 6.4-- What is the
Prospects for Biological Weed Control? Exercise 6.5-- What is the Prospects for 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. |