A smoky discolouration of the undersides of the leaves if that first sign of speckle. The leaves yellow in the affected areas, and the characteristic dark-brown to black dots or speckles gradually develop.
Badly affected leaves may yellow all over and hang down around the pseudo-stem. Fruit production will be reduced.
Spores are spread by wind. Germination is more likely on the lower sides of leaves which are shaded and remain moist longer.