See:
Dianthus (Sweet William) - Leaf Spots
Cause Colletotricum sp. have been found many time from leaf spot samples sent into the OSU Plant Clinic. The fungus C. dematium has been reported from Washington. The old-fashioned 'Sweet William' cultivars seem to tolerate this disease with only minor damage, but several other cultivars are highly susceptible. Spores of the fungus are spread by splashing water and by handling operations in the greenhouse or by wind and splashing water in the landscape.
Symptoms Lower leaves develop irregular spotting and blighting which later turns brown. Infected leaves and stems show characteristic black dots (acervuli) where spores are formed. The black dots have small black needle like structures (setae) surrounded by a mass of spores. All lower leaves may turn brown and, if left unchecked, the infection may move into the main stem, causing collapse of the entire plant.
Cultural control
- Take cuttings from pathogen-free plants.
- Remove and destroy infected plant parts.
- Rotate plantings.
- Avoid overhead irrigation, or irrigate so that leaves are not wet for extended periods.
Chemical control Fungicides work best when applied during active plant growth but before symptoms develop and before wet weather is expected.
- Armada 50 WDG at 3 to 9 oz/100 gal water. Do not use a silicone-based surfactant. Not for nursery or greenhouse use. Group 3 + 11 fungicide. 12-hr reentry.
- Avelyo at 3 to 5 fl oz/100 gal water. Group 3 fungicide. 12-hr reentry.
- Banner MAXX at 5 to 8 fl oz/100 gal water. Group 3 fungicide. 12-hr reentry.
- Broadform at 4 to 8 fl oz/100 gal water. Group 7 + 11 fungicide. 12-hr reentry.
- Compass 50 WDG at 2 to 4 oz/100 gal water. Do not use organosilicate additives. Group 11 fungicide. 12-hr reentry.
- Daconil Weather Stik at 1.38 pints/100 gal water. Avoid blooms. Group M5 fungicide. 12-hr reentry.
- Disarm 480 SC at 1 to 4 fl oz/100 gal water. Group 11 fungicide. 12-hr reentry.
- Fame SC at 1 to 4 fl oz/100 gal water. Group 11 fungicide. 12-hr reentry.
- Heritage at 1 to 8 oz/100 gal water plus a non-silicone-based wetter sticker. Group 11 fungicide. 4-hr reentry.
- Monterey Liqui-Cop at 3 Tbsp/gal water. H
- Mural at 4 to 7 oz/100 gal water. Group 7 + 11 fungicide. 12-hr reentry.
- Nu-Cop 50 DF at 1 lb/100 gal water. 48-hr reentry general or 24-hr reentry for greenhouse.
- Ortho Rose & Flower Disease Control at 2 fl oz/gal water. Group 3 fungicide. H
- Pageant at 8 to 12 oz/100 gal water. Do not use with organosilicone-based adjuvants. Group 7 + 11 fungicide. 12-hr reentry.
- Spectracide Immunox Multi-Purpose Fungicide Spray Concentrate for Gardens at 1 fl oz/gal water. Group 3 fungicide. H
- Tourney EZ at 1 to 4 oz/100 gal water. Group 3 fungicide. 12-hr reentry.
- Trinity at 4 to 12 fl oz/100 gal water. Group 3 fungicide. 12-hr reentry.
Reference Creswell, T. 2021. Dianthus Anthracnose. Purdue University Landscape Report. Issue 21-06.