Plants were sampled monthly for three years in a horticultural area in central Spain within three habitats characterised by different degrees of human intervention: fallow fields, edges between fields, and wastelands. Plants were sampled systematically along fixed itineraries, with no consideration of symptom expression, as described in Sacristán et al. [21] . Infection by AMV, BWYV, CMV, WMV and TSWV in the sampled plants was analysed by double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA), using commercial antisera (Bio-Rad, Marnes-La-Coquette, France), according to the manufacturer's instructions.