IVERMECTIN POUR-ON FOR CATTLE - EFFECTS ON SOME DUNG-INHABITING INSECTS

Dung from two steers treated with the recommended therapeutic dose of a pour-on formulation of ivermectin was bioassayed with the horn fly H aematobia irritans (L.) and the introduced dung beetles Euoniticellus intermedius (Reiche) and Onthophagus gazella (F.). Emergence of adult horn flies reared on dung from the treated steers was significantly re duced for 5-6 wk compared with emergence of flies reared on dung from an untreated steer. There were no effects on mean numbers of brood bal ls produced by either dung beetle species. However, emergence of adult E. intermedius and O. gazella from brood balls made with dung from tr eated steers was reduced for 1-2 wk and 2-3 wk, respectively.