Thanks for the warning Giles, the flower scape is currently 2 1/2 inches and showing no signs of fungus, yet! In previous years, the scapes on many of my small, terrestrial Utrics have been attacked by a white, powdery fungus (mildew?), which whilst unsightly, doesn't seem to affect the flowers. For some reason, there is no sign of this fungus this year, so hopefully things might be O.K. At the first sign of any fungus on my U. tricolor, I'll be ready with the fungicide spray!, it seems there is nothing to lose by trying to zap it.
Cheers
Vic