The struggle to control populations of organisms that feed on agricultural crops, livestock, and directly on humans is as old as recorded history, and will continue into the perceivable future. Only 30 years ago, the availability of relatively cheap and highly effective synthetic organic pesticides was thought to be the ultimate solution to pest populations. However, our naïveté regarding the ability of pest populations to rapidly adapt to simplistic man-induced selection pressures has become increasingly apparent, as have the detrimental impacts of pesticides on the environment. The evolution of the integrated pest management paradigm can be traced to these concerns, and it is now accepted that sustainable solutions to the management of pest populations will only be borne out of an increased understanding of the functioning of ecosystems. Knowledge of the population dynamics, and underlying causes of density changes in pest populations, behavioural ecology, and population genetics of pests and natural enemies, are essential elements for designing appropriate biologically intensive strategies for pest management. Progress is being made, and several examples of innovative strategies and promising areas of research, are discussed. Future work must continue to be based on a solid foundation of ecological understanding, to avoid the pitfalls of simple opportunistic solutions.

Significant changes have occurred in the role of pesticides in pest management programmes since the publication of Carson's book Silent Spring in 1962. This discourse addresses the multitude of factors which contributed to these changes including such factors as policy and legislation, the public's perception of associated risks, population pressures, the availability of practical integrated pest management programmes, and perhaps most importantly, the constraints to IPM in Third World countries. While reliable statistics are difficult to obtain, the changing patterns in pesticide use in the tropical regions are also discussed. Finally, the future of pesticide use in developing countries is projected, as is the necessity of their use and expected impacts.

Pesticides provide an important component of integrated pest management, but the timing, accuracy of dosage, and method of applying the pesticides need careful consideration to permit harmonisation with other control tactics. Concern about pesticide spray drift has led to categorising the spray quality of nozzles, which is defined by comparing the droplet spectra of selected reference nozzles measured with a laser light diffraction analyser. However, there is a conflict between a need for small droplets for increased biological efficacy and large droplets to reduce downwind drift. Registration authorities tend to favour a coarser spray with large droplets, and an untreated barrier area that can be left around a treated crop to protect sensitive crops downwind that can provide a refuge for natural enemies. In some circumstances, drift can be reduced with small droplets by electrostatically charging a spray. The charged spray needs to be released close to the crop to avoid the upward dispersion of droplets within a spray cloud due to mutual repulsion exacerbated by convective air movement. Increased deposition of charged sprays on the crop foliage is associated with less soil contamination which allows greater survival of ground-dwelling predators. This feature needs to be exploited by growing relatively narrow strips of a range of crops so that if one crop needs a pesticide treatment, natural enemies can be conserved in adjacent untreated crops. By careful selection of insecticides and dosage rates, these predators should be able to recolonise the treated area and thus integrate chemical with biological control. Application of more selective mycopesticides may require special formulations as well as particular droplet spectra. Pesticides can also be applied mixed with attractants such as pheromones, as a ‘lure and kill’ technique.

Species diversity of animals and plants is relevant to pest management in very different ways. Plant diversity provides sources of biologically active natural products and of genes for plant resistance. Animal diversity is involved in both harmful and beneficial interactions between crops and weeds or uncultivated land and in provision of potential biological control agents. The pest management implications of changes in biological diversity therefore need to be considered at a smaller scale in the management of cropping systems and on a larger scale in development programmes and national land use planning.

Crop losses caused by pests are a major problem in both developed and developing countries. Increasing awareness of the environmental consequences of indiscriminate use of chemical pesticides has provided new impetus for the search for alternative ways of managing pests. Particular emphasis has been placed on strategies that cause less pollution to the environment and those that are affordable, especially for the less developed countries. One concept that has received a lot of attention is integrated pest management (IPM), which seeks to manage pests and minimise crop losses by using methods that are economically viable and less harmful to the environment.

At least three distinct classes of new biotechnologies can have impacts on integrated pest management. These include microbial biotechnologies, plant molecular biology and genetics, and insect molecular biology and genetics. For example, recent advances in molecular biology have enabled scientists to overcome species barriers and to genetically alter plants, animals and microorganisms in ways that were not possible before. Already, several genetically altered plants which express genes that confer protection against pests have been produced. The techniques of biotechnology have also played important roles in elucidating pest populations and in studying the population dynamics of biological control agents and other types of organisms that live in association with crop plants. This article examines some of the major developments in the areas of molecular biology, genetics and biotechnology and the potential impacts that they could have on integrated pest management worldwide.

This paper reviews major concepts and achievements made in the tropics in tackling; five major social and economic issues associated with research, development and adoption of integrated pest management technologies during the past two decades. Major focus has been placed on (i) integrating IPM into farming systems, (ii) monitoring pest populations, (iii) information and management intensity of IPM, (iv) economic viability of IPM, and (v) institutional factors affecting IPM. Emphasis is placed on pinpointing ways in which success can be achieved and how constraints can be overcome in order to make IPM work better in future.

This paper examines social and economic aspects of integrated vector management in relation to the control of various vector-borne human diseases. The role of the human environment and activities in transmitting and in controlling human diseases is described. Common vector-borne human and domestic animal diseases in the tropics are listed and described in relation to their carriers (vectors), geographical regions of prevalence, approximate numbers of humans affected and likely remedial strategies. The benefits of integrated vector control as opposed to chemical control are discussed and supported with examples from various parts of the world. The paper ends by listing World Health Organisation recommendations on how to control human vector-borne diseases.