Effects of certain anthelmintics on the survival and reproduction of Euoniticellus intermedius (Reiche) (Coleoptera : Scarabaeidae)

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.