A new potyvirus, Zantedeschia mild mosaic virus (ZaMMV), was recently identified in calla lily (Zantedeschia spp.) in Taiwan. The sequenced 3′-terminal region indicated a unique amino acid sequence of ZaMMV, the N terminus of the capsid protein (CP), containing 39 glutamine residues before the DAG motif. In order to obtain antiserum for subsequent studies, a recombinant ZaMMV CP without polyglutamine was successfully expressed in Escherichia coli and used as the antigen. The specificity of ZaMMV antiserum was confirmed by immunoblot and ELISA analyses. Three detection methods, ELISA, dot-blot hybridization and immunocapture reverse transcription PCR (IC-RT-PCR), were developed and were able to detect ZaMMV successfully. During 2003–2004 field surveys, the results demonstrated that ZaMMV, as well as Zantedeschia mosaic virus (ZaMV), are prevalent in calla-growing areas. In contrast, infection by Dasheen mosaic virus (DsMV), the most important virus of aroid plants, decreased dramatically because DsMV-free calla lily seedlings were grown in the field. Accordingly, the detection methods developed in this study will be useful in studying ZaMMV and also in producing ZaMMV-free calla lilies.