The potential for avermectins to affect wildlife.

Avermectin residues in the dung from treated livestock are detrimental to dung insects. Rare insects could be put at risk by the use of avermectins, especially those which breed exclusively in the dung of the herbivores on which avermectins are used. Livestock dung is an important feeding habitat for a number of vertebrate species. The potential for direct poisoning of vertebrates through the accumulation of avermectins in the body, after consumption of invertebrates containing residues, would, on present knowledge, appear to be limited, but should not be disregarded. The use of avermectins may also indirectly affect some species of vertebrate by depleting the quality and quantity of important food resources. The effects of any reduction in invertebrate food in livestock dung would be expected to be especially severe if it occurred at critical times for the vertebrates, such as during the breeding season or when newly independent young animals were foraging and fending for themselves. Insects that develop in livestock dung therefore have important, additional roles in the ecology of pasture-lands, other than aiding dung degradation processes. It is essential that these other roles are taken into account when any assessment of the environmental consequences of using avermectins in livestock is being made.