FATE AND EFFECTS OF PESTICIDES UNDER TROPICAL FIELD CONDITIONS $$$$ IMPLICATIONS FOR AND RESEARCH NEEDS IN A DEVELOPING COUNTRY

摘要

Public concern over the impact of pesticides on public health and on the quality of the environment is of importance in Central America and Panama. The main problems of pesticide use are the direct effects on health, mainly of applicators, and the side effects on non-target organisms and the environment. Important among the data that are needed to reduce the environmental risks potentially associated with pesticide use is a clear understanding of the environmental processes. Much of this information has been generated in the ecosystems of developed countries. Therefore, prediction of the environmental fate of a pesticide can be made using mathematical models and the physical and chemical properties of a given chemical; for example, volatilization and pesticide losses can be predicted in terms of the vapour pressure of the chemical and the nature of the surface. However, the agricultural system and the method of application are also important. These are complex parameters, which are sometimes specific to a region. The knowledge gained in laboratory and outdoor experiments carried out in temperate zones on the behaviour and effects of a pesticide cannot be transferred with certainty to a complex, dynamic, natural tropical ecosystem. Regional conditions may therefore be covered by selecting key pesticides, soils and research techniques, including simple methods and analytical techniques. Environmental monitoring plays an essential role in the evaluation and management of agrochemicals, and leaching has been recognized as a problem in certain cases. Between 1990 and 1995, the behaviour of various herbicides and insecticides was analysed under tropical field conditions. Taking into account the local practices and the environmental conditions, an evaluation is being made of widely used key pesticides using microecosystems, lysimeters, and radioisotopes and related techniques. The studies have yielded additional, useful data on the dissipation of pesticides (propanil, atrazine, maneb and carbofuran) in agricultural soils under tropical field conditions.