Effects of ivermectin in dung pats on earthworm (Megascolecidae) populations and pat degradation in Japanese grassland S. Kaneda a , N. Yamashita a, * , T. Uchida a , S. Shimano a , N. Miyoshi a , M. Sasaki b , Y. Enami c a Department of Upland Farming, National Agricultural Research Center for Tohoku Region, Arai, Fukushima-city 960-2156, Japan b Fukushima University, Kanayagawa, Fukushima-city 960-1293, Japan c Shiga Prefecture Agricultural Reserch Center, Agricultural Experiment Station Dainaka 516 Azuchi-cho, Gamou-gunn, Shiga 521-1301, Japan Received 18 January 2005; received in revised form 27 April 2005; accepted 3 May 2005 Abstract The effects of residual ivermectin in dung pats on earthworm activity and dung decomposition in Japanese grassland, where Megascolecidae are the dominant group of dung decomposers, were studied. Artificial cowpats containing 0, 0.1, and 1 mg ivermectin kg À1 dung were prepared and deposited on grassland in October 2003. Pats were collected again for analysis 1, 3, 5, and 7 weeks after deposition. Earthworms were collected from the soil around pats at a depth of 0–10 cm. The Megascolecidae, Pheretima (Amynthas) heteropoda and Pheretima (Amynthas) divergens, together accounted for more than 90 and 99% of earthworm individuals and biomass, respectively. Earthworms aggregated around the pats regardless of the ivermectin treatment. Dung-degradation rate was also unaffected by the ivermectin treatments. Dung decomposition appeared to be due mainly to earthworm activity, as dung beetles were rare at this site. These results suggest that ivermectin may have no adverse effects on Megascolecidae activity and on the degradation of cowpats in pastureland sites where earthworms dominate the dung decomposer community. # 2005 Elsevier B.V. All rights reserved. Keywords: Anthelmintic; Dung pats; Megascolecidae; Pat degradation; Ivermectin; Earthworms 1. Introduction Ivermectin efficiently controls parasitic gastroin- testinal and pulmonary nematodes, mites, lice, warble flies and ticks at a low dosage (Campbell et al., 1983). The drug is also a potent insecticide against dung- breeding parasitic insects (Strong, 1992). An out- standing feature of the drug is its persistent activity. Most of the ivermectin is ultimately excreted in the feces of livestock as a mixture of the original drug and its metabolites. Thus, the use of ivermectin as an anthelmintic in free-range livestock might have negative effects on non-target invertebrates, such as dung beetles and earthworms, which feed on dung and www.elsevier.com/locate/apsoil Applied Soil Ecology 31 (2006) 280–285 * Corresponding author. Tel.: +81 24 593 6173; fax: +81 24 593 2155. E-mail address: yama@affrc.go.jp (N. Yamashita). 0929-1393/$ – see front matter # 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.apsoil.2005.05.001