Cause Curvularia gladioli (formerly Curvularia lunata), a fungus that has been reported from Oregon on gladiolus The disease is favored by warm, wet conditions. Optimum fungal growth is from 75 °F to 85°F; infection occurs after a 13-hour dew period. Leaf spots may show up 4 to 5 days after infection. The fungus can survive on infected corms or in soil at least 3 years. Many cultivars are fairly resistant, but Picardy is very susceptible.
No cultivars are immune but the more tolerant cultivars include Amsterdam, Friendship Rose, Gold Yester, Tradehorn and Veronica.
Symptoms Leaves, stems, and petals are affected. At first, light to dark brown, oval spots are seen most frequently on the leaf. These become oval to circular, brown spots with dark edges and surrounded by a yellow halo. Lesions become necrotic with leaves looking dry and wilted. The fungus produces a black, powdery mass of spores in the center of the spot.
Cultural control
- Long rotations greater than 3 years may be helpful.
- Plant tolerant cultivars.
- Rake and burn leaves in fall.
- Destroy infected corms.
Chemical control Spray during warm, wet weather.
- Bonide Fung-onil Multi-purpose Fungicide at 2.25 teaspoons/gal water. Group M5 fungicide. H.
- Daconil Weather Stik at 1.38 pints/100 gal water. Group M5 fungicide. 12-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. Reduce the rate to 0.75 lb/100 gal water for flower spikes.
- Protect DF at 1 to 2 lb/100 gal water plus 2 to 4 oz spreader-sticker.
- Monterey Liqui-Cop at 3 Tbsp/gal water. H
- Ortho MAX Garden Disease Control at 2 teaspoons/gal water. H
- Spectro 90 WDG at 1 to 2 lb/100 gal water. Group 1 + M5 fungicide. 12-hr reentry.
Reference Torres, D.P., Silva, M.A., Pinho, D.B., Pereira, O.L., and Furtado, G.Q. 2013. First report of Curvularia gladioli causing a leaf spot on Gladiolus grandiflorus in Brazil. Plant Disease 97:847-847.