A White Blister-rust affecting various plants in the Brassicaceae family (crucifers) including cultivated brassicas, Honesty, Shepherd's Purse, Bittercress, Hedge Mustard, Charlock and many more species.  Plants have a crusty white coating over leaves and stems, causing galls and thickening and distortion of the stem, leaves and fruits.  This is a complex of species - see 'Further Information' below and Chater et al (2020) for more details.

host

Photograph the blister-rust on the host plant; ensure you have noted the host species in the comments

On various crucifers,

Summer.

The species complex includes the following species - for more information, see Chater et al (2020)

• Albugo candida sensu stricto affect a number of species but is most commonly recorded on Shepherd's Purse (Capsella bursa-pastoris).  Other host plants include garden Arabis, Thale-cress (Arabidopsis thaliana), Aubrieta and Whitlow-grass (Erophila).
• Albugo hohenheimia affects Hairy Bitter-cress (Cardamine hirsuta)
• Albugo laibachii affects Thale cress
• Albugo leimonea affects Cuckoo-flower or Lady's-smock (Cardamine pratensis)
• Albugo rorippae affects Yellow-cresses (Rorippa)