Contamination of wildlife with DDT insecticide residues in relation to tsetse fly control operations in Zimbabwe

The distribution of DDT insecticide residues in the environment of western Zimbabwe was surveyed in order to identify the major source(s) of DDT pollution and assess whether residue accumulation in wildlife is sufficient to cause deleterious biological effects. The most important source of DDT contamination in 1982/83 was the tsetse fly control programme, with relatively minor contributions made by mosquito control, commercial agriculture and traditional farming. Although it was shown that DDT residues do not persist in the non-living environment (tree bark, soil, riverine silt), they readily accumulate in insectivorous birds and bats (respective maxima: 32 and 20 μg g⁻¹ wet weight total DDT in viscera) and, to a lesser extent, in detritivorous mussels and piscivorous fish (maxima: 1·0 and 2·2 μg g⁻¹ in whole body and ovary, respectively). These residues are sufficient to cause eggshell thinning in certain avian predators.