Cause Alternaria nobilis (formerly Alternaria dianthi) ,a fungus that has been reported from Washington and found by the OSU Plant Clinic. It survives in plant debris and produces many airborne spores. High moisture, crowded plants and low fertility favor the disease.
Symptoms Small purplish circular-to-oval spots form on leaves. The center of the leaf spot becomes reddish-brown and a yellow border develops around the leaf spot. Spots may coalesce while the area between spots yellows. May also occur at the base of the petiole and girdle the leaf stem. Stem joints can also become infected eventually killing whole stems and/or the entire plant. Lower leaves may show symptoms first. Root and collar rot is also possible on rooted cuttings.
Cultural control
- Remove old leaves from growing area.
- Maintain good air circulation by spacing out plants.
- Avoid overhead irrigation or any practice that keeps plants wet for extended periods.
Chemical control Use foliar sprays along with cultural controls.
- 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. Not for use in the greenhouse. Group 3 fungicide. 12-hr reentry.
- Bonide Captan 50 WP may be used in home gardens at 1.5 Tbsp/gal water. H
- Captan 80 WDG at 1.5 lb/100 gal water. Group M4 fungicide. 48-hr reentry.
- Chipco 26019 FLO at 1 to 2.5 quarts/100 gal water. Limit to two (2) applications per year to aid resistance management. Group 2 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.
- Eagle 20 EW at 6 to 12 fl oz/100 gal water. Group 3 fungicide 24-hr reentry.
- Heritage at 1 to 8 oz/100 gal water plus a non-silicone-based wetter sticker. Group 11 fungicide. 4-hr reentry.
- Mancozeb-based products. Group M3 fungicides. 24-hr reentry.
- Fore 80 WP at 1.5 lb/100 gal water plus a spreader-sticker.
- Protect DF at 1 to 2 lb/100 gal water plus 2 to 4 oz spreader-sticker.
- Medallion WDG at 1 to 2 oz/100 gal water. Use with oils or adjuvants may damage plant. Group 12 fungicide. 12-hr reentry.
- Monterey Liqui-Cop at 3 Tbsp/gal water. Discolored foliage or blooms have been noted. H
- Nu-Cop 50 DF at 1 lb/100 gal water. Discolored foliage or blooms have been noted. Group M1 fungicides. 48-hr reentry. O
- Orkestra at 4 to 6 fl oz/100 gal water. Group 7 + 11 fungicide. 12-hr reentry.
- Ortho MAX Garden Disease Control at 2 teaspoons/gal water. H
- Pageant at 4 to 8 oz/100 gal water. Do not use with organosilicone-based adjuvants. Group 7 + 11 fungicide. 12-hr reentry.
- Spectro 90 WDG at 1 to 2 lb/100 gal water. Group 1 + M5 fungicide. 12-hr reentry.
- Spirato GHN at 1 to 2 fl oz/100 gal water. Use with oils or adjuvants may cause plant damage. Group 12 fungicide. 12-hr reentry.
- Terraguard SC at 4 to 8 fl oz/100 gal water. Group 3 fungicide. 12-hr reentry.
- Tourney EZ at 1 to 4 oz/100 gal water. Group 3 fungicide. 12-hr reentry.
- Trinity at 4 to 8 fl oz/100 gal water. Group 3 fungicide. 12-hr reentry.
- Ziram 76 DF at 1.5 to 2 lb/100 gal water. Group M3 fungicide. 48-hr reentry.
Reference Strider, D.L. 1978. Alternaria blight of carnation in the greenhouse and its control. Plant Disease Reporter 62:24-28.
Wolcan, S.M., Malbran, I., Mourelos, C.A., Sisterna, M.N., Gonzalez, M.P., Alippi, A.M., Nico, A., and Lori, G.A. 2017. Diseases of Carnation. In McGovern, R.J., and Elmer, W.H. (eds.) Handbook of Florists' Crops Diseases. Springer Int.