columbine downy mildew

Symptoms

Pale yellow blotches appear on the upper leaf surface with a grey-purple downy mould directly beneath them on the underside; affected leaves curl, distort and brown, new growth is stunted and twisted, and badly infected plants collapse and die. The grey down on the leaf underside under yellow upper blotches is the tell.

Easily confused with

• Columbine powdery mildew

  How to tell them apart: Both Erysiphe aquilegiae (columbine powdery mildew) and Peronospora aquilegiicola (columbine downy mildew) coat Aquilegia leaves with a 'mould', but in opposite ways. Powdery mildew is a dry, white-grey, mealy dust mainly on the UPPER leaf surface that wipes off with a finger, spreads in warm humid weather, and leaves the leaf shape intact at first. Downy mildew shows a greyish-violet, felty fuzz on the LOWER surface only, sitting beneath angular yellow-to-purple blotches that are bounded by the leaf veins; the foliage becomes distorted, pale and overlong, leaves curl, brown and collapse, and it spreads in cool, wet conditions. If the bloom is on top and rubs off = powdery mildew; if it is underneath with vein-limited discoloured patches and twisted leaves = downy mildew.