See:
Amaryllis (Hippeastrum) - Leaf Scorch (Red Leaf Spot)
Cause Peyronellaea curtisii (formerly Stagonospora curtisii), a fungus that survives on the necks of bulbs and on infested foliage. Leaves and flower stalks may be injured as they push up between bulb scales. Under moist or humid conditions, spores infect the plant through these injuries or other wounds. Cultivars vary in resistance but it is reported as a common problem on Grand Soleil d'Or and Magnificence.
Symptoms Yellow-red or brown spots appear on the top 2 to 3 inches of leaves as or soon after they emerge from the soil. A yellow band separates diseased from healthy tissue. Small, water-soaked spots with yellow centers appear in discolored leaves or on adjacent leaves. Surrounding tissue dies and turns light grayish-brown around the brown spots, which become raised and scabby. Brown fungal fruiting bodies (pycnidia) appear in the scabby areas. Lesions can coalesce with rapid foliar dieback soon after spots appear. Lesions remain visible even after leaves collapse and dry. Spots can occur on leaves, flower stalks, spathes, and flowers but the fungus does not cause a bulb rot. Symptoms sometimes are mistaken for those of frost or herbicide injury.
Cultural control
- Rotate to a new planting site each year.
- Remove and destroy infected plants.
- Wash equipment and machinery between fields.
Chemical control Tank-mix or rotate fungicides from different groups that have different modes of action for resistance management.
- Aldesan Microbiocide at 2 fl oz/gal of water and heat to 110°F to 111°F for 4 hours. Change dip tank water when it becomes discolored or when sediment is present. Dip dank wastewater may be applied to bulb fields when rain is not expected for 24 hours. Washington only. SLN WA-160001b. Formaldehyde Solution 37 is also registered with SLN WA-160001.
- Bonide Fung-onil Multi-purpose Fungicide at 2.25 teaspoons/gal water. Group M5 fungicide. H
- Bordeaux 8-8-100. Group M1 fungicide. O
- Broadform at 4 to 8 fl oz/100 gal water. Group 7 + 11 fungicide. 12-hr reentry.
- Chipco 26019 FLO at 1 to 2.5 quarts /100 gal water. Group 2 fungicide. 12-hr reentry.
- CuPRO 5000 at 1.5 to 2 lb/A. Group M1 fungicide. 48-hr reentry.
- Daconil Weather Stik at 1.38 pints/100 gal water. Group M5 fungicide. 12-hr reentry.
- Insignia SC at 3 to 6 fl oz/100 gal water. Do not use with organosilicate-based adjuvants. Group 11 fungicide. 12-hr reentry.
- Mural at 4 to 7 oz/100 gal water. Group 7 + 11 fungicide. 12-hr reentry.
- Orkestra at 8 fl oz/100 gal water. Group 7 + 11 fungicide. 12-hr reentry.
- Pageant at 12 to 18 oz/100 gal water. Do not use with organosilicone-based adjuvants. Group 7 + 11 fungicide. 12-hr reentry.
- Palladium at 4 to 6 oz/100 gal water. Avoid excessive runoff to small plants, which may result in stunting and/or chlorosis. Group 9 + 12 fungicide. 12-hr reentry.
- Spectro 90 WDG at 1 to 2 lb/100 gal water. Group 1 + M5 fungicide. 12-hr reentry.
- Thiophanate-methyl-based products. Group 1 fungicides. 12-hr reentry.
- Cleary's 3336 EG at 12 to 16 oz/100 gal water.
- OHP 6672 4.5 F at 10 to 14.5 fl oz/100 gal water.
Reference Hanks, G.R. and Chastagner, G.A. 2018. Diseases of Daffodil (Narcissus). In McGovern, R.J. and Elmer, W.H. (eds.) Handbook of Florists' Crops Diseases. Springer Int.
Smith, C.O. 1934. Inoculations of Stagnospora curtisii on the Amaryllidaceae in California. Phytopathology 25:262-268.