Abstract:
Avermectins and milbemycins are commonly used in agro-ecosystems for the control
of parasites in domestic livestock. As integral members of agro-ecosystems with importance
in maintaining pasture health through dung burial behaviour, dung beetles are an excellent,
non-target, bio-indicator taxon for examining potential detrimental effects of pesticide
application. The current study uses the dung beetle species, Euoniticellus intermedius
(Reiche), as a bio-indicator to test the relative toxicity of four different anthelmintics in dung
residues. There have been numerous laboratory and field trials on these four anthelmintics
but there has never been a laboratory trial comparing ivermectin, eprinomectin, doramectin
and moxidectin under precisely the same conditions. The effects of avermectin and
milbemycin toxicity are not confined to parasitic nematodes and arthropods, but also extend
to a large variety of beneficial invertebrate species, which use the dung as a microhabitat and
breeding resource. Over time, pesticide usage indirectly affects the rate of dung degradation
through adverse effects on dung beetles. This potential problem constitutes the main focus of
this study. The present and previous studies have indicated no significant effect on the
survival of adults but a significant reduction in reproductive rate and reproductive success.
Over time, reduced reproductive rate would result in decreased population sizes in the dung
beetle community and, ultimately, a decrease in the rate of dung degradation and dung
burial. It is, thus, vitally important to create awareness about the importance of dung beetles
and sound farming practices for healthy agro-ecosystems.
