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Integrated pest management (IPM) should be based on sound ecological principles. It requires knowledge of the interaction between the fauna (pests and their natural enemies) and its environment. This paper attempts to review some of the interactions between pests and the cotton agroecosystem.
The pests considered are: pink bollworm (Pectinophora gossypiella Saund.), the Heliothis/Helicoverpa complex, sweet potato whitefly (Bemisia tabaci Genn.), cotton aphid (Aphis gossypii Glover) and boll weevil (Anthonomus grandis Boh.). Ecological attributes that are of significance to pest management are discussed. They include: adaptation to adverse conditions through diapause, search for suitable host plants through dispersal and migration; reproduction and the role of pheromones, growth and development in relation to climate and the presence of wild and cultivated hosts; and natural enemies (insects and pathogens).
The second part concerns the ecology of cotton-based farming systems. Pest control strategies should be based on a clear understanding of the growth and development pattern of cotton; of other crops that are grown before and after a cotton crop or in its vicinity; and of local wild plant species. Weather and climate have to be considered for selecting the site, planting dates, cultivars, and mode of application of plant growth regulators. Fertilizers can affect growth and development of certain pests also. Management of crop residues is a key factor that influences survival of overwintering species.
The ability of pests to counter individual control measures underscores the importance of developing a larger arsenal of crop protection techniques based on crop and pest ecology. A multidisciplinary approach offers the only possibility of anticipating the consequences of disruptive practices, such as change in cultivars and cultural practices, in the same way as efforts to counter the non-intentional effects of pesticide applications.
Pest control requires knowledge of ecological principles. All possible factors, both natural and artificial, that could be used to combat crop pests must be considered. We cannot disregard the capability of pests to counter control strategies. Hence, IPM requires the forming of teams of scientists capable of taking a broad ecological overview of the pest problems associated with the cotton agroecosystem and willing to develop unified, ecologically based approaches to cotton pest control. Only such multi-disciplinary teams will have the potential for developing effective, economical and sustainable solutions for cotton pest problems, by approaching the cropping system as an ecological unit.
IPM strategies remain conditioned by our limited understanding of the biology of the pests, their mobility and interactions, and the shifting germplasm of the cotton crop. A holistic approach provides new insight into the complexity of interspecific relationships of arthropods in the agroecosystem; the major natural enemies and other factors that determine the abundance of key, occasional and potential pests.
The forming of teams whose members include specialists in crop protection and other disciplines should prevent the emergence of ‘single answer’ control measures. An IPM approach will provide alternative solutions in the event of ‘crises’, such as the emergence of pesticide-resistant strains, biotypes that overcome plant-resistance traits or the arrival of a new species in an ecosystem.
Cotton insect management problems observed recently in various parts of the world, would probably be a good illustration of these principles. It appears that the areas concerned are located either in countries with high level of intensification, or when small scale farmers have an unlimited access to pesticides. This suggests that we would probably have to widen our subject to the human factor. Farmers themselves have to be considered as a part of the “ecological attributes” of major cotton pests.
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