A comparison of the development and survival of the dung beetle, Onthophagus taurus (Schreb.) when fed on the faeces of cattle treated with pour-on formulations of eprinomectin or moxidectin

Faeces voided by 1-year old cattle at 3-70 days after treatment with a pour -on formulation of moxidectin had no detectable effects on development or s urvival of the common dung beetle Onthophagus taurus. In contrast, faeces v oided by cattle treated with a pour-on for-mutation of eprinomectin were as sociated with high juvenile mortality during the first 1-2 weeks after trea tment. Increased mortality also occurred among newly emerged beetles fed on faeces collected 3 days after eprinomectin treatment and there was evidenc e of suppressed brood production among those that survived. This effect was still apparent even after insects fed for a further 10 days on the faeces of untreated cattle. A model simulating the effects of drug residues on dun g beetle populations suggests that in the absence of immigration a single t reatment of eprinomectin is capable of reducing beetle activity in the next generation by 25-35%. Effects are likely to be greatest when treatment coi ncides with emergence of a new generation of beetles. (C) 2001 Elsevier Sci ence B.V. All rights reserved.