Probably oligolectic on Asteraceae; all pollen samples available so far consist of pollen of Carduoideae (A. Müller, unpublished, based 15 pollen samples from 13 different localities).
Müller (2018) in a further study (based on 30 pollen samples from 22 different localities from across the distribution range) showed that all pollen loads analysed contained exclusively Centaurea pollen. Osmia padri is likely a specialist of Carduoideae.
Visitation records: Carduus sp. (Zanden, 1983), Centaurea arenaria (Tkalců 1979), Centaurea solstitialis (Asteraceae)(Tkalců 1979) (all cited in Müller, 2018)