Cause Fungi: Stagonosporopsis aquilegiae (formerly Ascochyta aquilegiae) has been reported from Idaho and found by the OSU Plant Clinic; Cercospora aquilegiae has been reported from Oregon, but Septoria aquilegiae has not been reported from the Pacific Northwest. These fungi survive in old infected leaf debris. Conditions that keep foliage wet for extended period generally favor the fungi.
The OSU Plant Clinic has also found a Pseudomonas sp. associated with black leaf spots.
Symptoms Ascochyta produces dark areas on the leaf with purple margins. Cercospora produces circular to elliptical spots that are reddish brown to black. Conidia may be found on both sides of the leaf.
Cultural control
- Space plants for good air circulation.
- Keep leaves dry by avoiding overhead irrigation or timing irrigation so leaves dry quickly.
- Remove and destroy infected leaves and leaf debris.
Chemical control
- Eagle 20 EW at 6 to 12 fl oz/100 gal water. Labeled for rust control and may be effective on several leaf spots. Group 3 fungicide. 24-hr reentry.
- Myclobutanil 20 EW T&O at 6 to 12 fl oz/100 gal water plus spreading agent. May observe a PGR effect. Group 3 fungicide. 24-hr reentry.
- Ortho Rose & Flower Disease Control at 2 fl oz/gal water. Group 3 fungicide. H
- Protect DF at 1 to 2 lb/100 gal water plus 2 to 4 oz spreader-sticker. Group M3 fungicides. 24-hr reentry.
- Spectracide Immunox Multi-Purpose Fungicide Spray Concentrate for Gardens at 1 fl oz/gal water. Group 3 fungicide. H
Reference Laubert, R. 1930. Leaf spot disease of Columbine. Gartenwelt 34, no. 45.