PESTICIDES REPORT .38. PESTICIDE FATE IN TROPICAL SOILS - (TECHNICAL REPORT)

Pesticide use is an important component of agricultural and non-agricu ltural pest control in tropical areas. However, the fate of pesticides in tropical soils is not as well understood as that for soils from te mperate regions. Tropical soils defy easy generalizations, but they ar e typically very old soils characterized by year-round uniformity of t emperature regime. Although only a few studies have directly compared pesticide fate in tropical and temperate soils, there is no evidence t hat pesticides degrade more slowly under tropical conditions. Laborato ry studies in which soils have been held under standardized conditions reveal that pesticide degradation rate and pathway are comparable bet ween tropical and temperate soils. However. field investigations of tr opical pesticide soil fate indicate that dissipation occurs more rapid ly, in some cases much more rapidly, than for pesticides used under si milar temperate conditions. The most prominent mechanisms for this acc eleration in pesticide dissipation appear to be related to the effect of tropical climates, and would include increased volatility and enhan ced chemical and microbial degradation rates on an annualized basis.