See:
Gladiolus - Fusarium Yellows and Corm Rots
Cause The OSU Plant Clinic has found Fusarium spp. on several corm and root rot samples of Freesia. Several different Fusarium spp. have been isolated and shown to cause wilting and corm rots. All fall into the Fusarium oxysporum f. sp. gladioli category. These fungi live in soil and plant debris for many years as chlamydospores. Spores infect roots and cross the basal plate. These infections may continue to enter and spread within the vascular tissues. The fungus is spread widely by contaminated soil and latent infections of corms. Disease is favored by warm weather. Similar diseases occur on crocosmia, gladiolus, iris and several other crops.
Symptoms Infected corms may show no symptoms at all. Yellowing of the outer leaves is usually the first symptom observed followed by yellowing of the other leaves. Plants may be stunted and ultimately the leaves wilt and die. Small discolored spots, sometimes pinkish, may be seen on the outside of the corm. In cross section, reddish discolored of vessel elements may be seen inside the corm. During storage a dry rot develops with the entire corm rotting in some cases.
Cultural control
- Select clean planting stock and discard all diseased corms.
- Plant in clean soil and avoid wounding corms.
- Use a 4-year rotation.
- Cure corms quickly after digging and discard all diseased corms before storing.
Chemical control Treat within 48 hours of digging and drying.
- 42-S Thiram at 1.5 pints/8 gal water. Group M3 fungicide. 24-hr reentry.
- KleenGrow at 0.15 to 1.5 fl oz/gal water. Soak for 30 seconds and allow to drain.
- Medallion WDG at 8 oz/100 gal water. Soak sorted bulbs for 20 min then dry. Group 12 fungicide. 12-hr reentry.
- Mertect 340 F at 30 oz/100 gal water. Temperatures should be 55°F to 75°F. Soak bulbs 15 to 30 min, then let dry. Group 1 fungicide. 12-hr reentry.
- Thiophanate-methyl-based products as a postharvest soak at 80°F to 85°F. Soak clean bulbs 15 to 30 min. within 48 hours after digging. Group 1 fungicide. 12-hr reentry.
- Cleary's 3336 EG at 16 to 24 oz/100 gal water.
- OHP 6672 4.5 F at 16 to 20 fl oz/100 gal water.
References Rattink, H. 1985. Some aspects of the epidemiology of Fusarium oxysproum f. sp. gladioli on Freesia. In IV International Symposium on Flower Bulbs 177:85-91.
Taubenhaus, J.J., and Ezekiel, W.N. 1933. Fusarium wilt and corm rot of freesias. Botanical Gazette 95:128-142.