Polylectic. Radchenko (1979) found N. minutissimus to forage for both Centaurea and Erigeron (Asteraceae) pollen but to provision individual cells with only one pollen type.
Westrich (1989) reported N. minutissimus to visit Senecio, Centaurea and Erigeron (Asteraceae) and also Sisymbrium (Brassicaceae), Jasione (Campanulaceae), Sedum (Crassulaceae) and Thymus (Lamiaceae).
Mavromoustakis (1948; 1952) lists the following forage sources: Zygophyllum album (Zygophyllaceae); Teucrium polium, Thymus capitatus, Mentha longifolia (Lamiaceae); Echium sericeum (Boraginaceae); Sinapis (Brassicaceae); Eryngium creticum (Apiaceae); Polygonum equisetiforme (Polygonaceae); Tamarix (Tamaricaceae). He also reports that the species is abundant at Tamarix leaves attacked by a species of Coccidae (presumably searching for exudate).