Which internally seed-borne fungal disease of wheat (Ustilago nuda tritici) converts all floral spikelets of the earhead into a loose, black powdery mass of smut spores covered by a delicate silvery membrane?

Loose Smut is an internally seed-borne disease where dormant mycelium rests inside the wheat embryo; upon ear emergence, entire floral parts are transformed into black powdery chlamydospores that blow away in the wind.