Eprinomectin from a sustained release formulation adversely affected dung breeding insects

Eprinomectin is applied to livestock to control parasites. LongRange(r) is a new formulation of eprinomectin that releases residues into the dung of the treated animal for a period of at least 150 days. We tested the effect of these residues on insects developing in dung of treated cattle. Residues reduced the total number of insects in dung of cattle treated either 7, 14, 28, 56, 84, 112, and 140 d previously. Residues reduced the diversity of insect taxa in dung of cattle treated between 84 and 112 d previously. Chemical analyses subsequently documented residues of eprinomectin in dung of each collection period post-treatment at levels expected based on previously reported excretion profiles for this product. In summary, cattle subcutaneously injected with this product excreted residues that reduced dung-breeding insect emergence for 5 mo post-treatment. The consequences of these long-term non-target effects to pasture ecosystems are not known.