An assay to identify interactions between Citrus dwarfing viroid (CDVd) and Citrus tristeza virus (CTV) showed that viroid titer was enhanced by the coinfecting CTV in Mexican lime but not in etrog citron. Since CTV encodes three RNA silencing suppres- sors (RSSs), p23, p20 and p25, an assay using transgenic Mexican limes expressing each RSS revealed that p23 and, to a lesser ex- tent, p25 recapitulated the effect observed with coinfections of CTV and CDVd.