TRENDS & FUTURE POSSIBILITIES
In Biological Pest Control
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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 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.
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 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 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.