Wikipedia
Tristerix
Tristerix is a genus of mistletoe in the family Loranthaceae, native to the Andes from Colombia to Chile. They are a woody perennial usually occurring as an aerial parasite, often pollinated by hummingbirds. Recents phylogenetic studies of the 11 known Tristerix species divides the genus into 2 subgenera; Metastachys and Tristerix with 9 and 2 species, respectively (though this was not confirmed by ITS analysis).
The species T. aphyllus is a parasite of cacti in Chile. It is only known to grow on two species of columnar cacti: Echinopsis chilensis and Eulychnia acida. T. aphyllus is sometimes called the "cactus mistletoe." It should not be confused with the mistletoe cactus, which is an epiphytic cactus, and not a parasite.