Oligolectic on Asteraceae with a clear or even exclusive preference for Carduoideae (A. Müller, unpublished, based on 50 pollen samples from 18 different localities and on field observations). In contrast, Güler & Sorkun (2007) assume O. bidentata to be polylectic, harvesting pollen from eleven plant families. Müller (2018) in a further study based on 62 pollen loads from 27 different localitiesacross the range of the species reports that pollen loads consisted exclusively of Centaurea pollen except for two loads that additionally contained moderate quantities of thistle pollen, indicating that O. bidentata most probably restricts pollen harvesting to the subfamily Carduoideae. A single load contained small amounts of Onobrychis pollen (Fabaceae) beside Centaurea pollen, suggesting that the females very rarely also exploit pollen hosts other than the Asteraceae.
Müller (2018) also lists the following visitation data: Carduus sp., Centaurea stoebe (Tkalců 1974a); Arctium, Carduus sp., Centaurea iberica, Centaurea spinosa, Cirsium sp., Onopordum sp. (Asteraceae).
Banaszak & Romasenko (1989), copied by Stanisavljevic (2000), list the following genera as forage sources: Carduus, Centaurea, Onopordon, Xerantheum (Asteraceae)
Ivanov et al. (2005) also state that the species is Oligolectic on Asteraceae.