The effects of aerial spraying of endosulfan for tsetse fly control on aquatic invertebrates in the Okavango swamps, botswana

Abstract

The effects of ULV spraying of endosulfan from the air for tsetse fly control on aquatic invertebrates were studied in the Okavango delta, Northern Botswana, over a three-year period. Comparison of zooplankton numbers in a sprayed and an unsprayed lagoon revealed no changes in numbers or composition due to spraying. Major change in zooplankton numbers were associated with the rise and fall of water levels during the annual flood. Studies on invertebrate numbers in the periphyton on submerged macrophytes in sprayed and unsprayed areas revealed no differences in the major groups attributable to spraying. In the southern delta, where considerable changes in water level occur, there was a reduction in numbers of chironomid larvae during high water periods. It was concluded from these data, taken in conjunction with residue levels of the insecticide in water following spraying, that the low rates of application used were unlikely to cause substantial damage to freshwater invertebrate populations in the Okavango region.