As this is a parasitic species, all flower visits will be for nectar only.
Celary (1989) lists the following nectar sources in Poland: Anchusa officinalis, Echium vulgare (Boraginaceae); Trifolium arvense, Trifolium repens (Fabaceae); Lythrum salicaria (Lythraceae); Calluna vulgaris (Ericaceae); Thymus sp. (Lamiaceae); Knautia arvensis (Dipsacaceae); Solidago virgaurea, Carduus crispus, Centaurea scabiosa, Centaurea rhenana, Centaurea jacea, Taraxacum officinale (Asteraceae)
In Spain, Ornosa & Ortiz-Sánchez (2004) list the following plant families as providing forage: Asteraceae and Fabaceae.