Vector control technology and its relationship to the environment and wildlife.
Abstract
This paper is one of a number on the effects on wildlife of contamination of the environment by pesticides that were presented at a conference in England in July 1965 and are noticed in more detail elsewhere [RAE A 55 1062-1089]. The following is based partly on the author's summary. Whereas ecological biological and some chemical measures used against insect pests cause long-lasting or permanent changes in the environment, most pesticides cause only temporary or semi-permanent changes. The extent to which wildlife is affected by insecticides is determined by many factors, some of which are briefly discussed with reference to programmes employed against arthropod vectors of diseases of man and domestic animals in the United States, Africa and Asia. In the United States, where insecticides are widely used against vectors, the effect of some programmes for mosquito control on other animals were studied on a limited scale in California [cf. B 53 51, etc.]. In laboratory feeding trials carried out in the course of work in collaboration with J. O. Keith on the toxicity of five highly effective larvicides to mallard (Anas platyrhynchos), fenitrothion (Sumithion), azinphos-methyl (Guthion) and SD 7438 [toluene-a, a-dithiol bis(O, O-dimethyl phosphorodithioate)] did not harm the birds, whereas parathion and fenthion were highly toxic. Birds in outdoor pens that were given food containing 25 parts parathion or fenthion per million, which is the maximum contamination likely to occur in natural food from larvicidal treatments, ate less than birds given uncontaminated food and lost in weight, whereas birds receiving diets containing the other three larvicides gained. Birds quickly recovered when transferred from a fenthion diet to an uncontaminated one, and no mortality occurred until they had fed on the fenthion diet continuously for 28 days. Birds that died while on a diet containing parathion contained no or virtually no residues. Neither parathion nor fenthion harmed pinioned birds on ponds treated with them six times in three months at 4-5 times the rate used for mosquito control. Some data from current studies on residues and biological effects of parathion applied to duck marshes at normal and exaggerated rates [cf. 55 29] are included.