Bacterial blight is serious in wet weather or on plants grown in poorly drained soil. Infected areas are first irregular, water soaked spots that later dry out and turn brown. The whole leaf becomes involved and dies. A slimy exudate may be seen. Discard infected corms. No chemical control is listed.
Scab causes pale yellow water soaked lesions on the corms. The lesions turn brown or nearly black, become sunken and have a raised brittle margin. The lesions exude a gummy substance. Early symptoms on the leaves are raised reddish specks near the leaf bases. The neck of the plant rots and the plant falls over. Discard infected corms. No chemical control is listed.
Corm rot causes corky decay with sunken, reddish brown lesions. At low temperatures the lesions are covered with green mold. The disease originates where husks are attached to the corm. Avoid wounding corms and store them in a cool dry cellar at 35 to 45 degrees to prevent initial infections. Prompt curing and drying of corms is essential. Cure newly dug corms at 85 degrees for 10 to 15 days. Control this disease caused by Penicillium gladioli with benomyl.
Hard rot is a storage problem. The corms are mummified. Brown to purplish brown lesions form on the leaves. The lower part of the corm is most severely attacked. Discard infected corms.
Dry rot causes circular, sunken spots on the corms. Brown or black lesions on the corms run together and destroy the whole corm, especially in moist storage rooms. The husks or leaf bases of infected plants are discolored and brittle. Leaves from infected corms turn yellow and decay. Use a new planting area and discard infected corms. This problem is caused by Stromatinia gladioli.
Botrytis dry rot causes corm rot and leaf and flower spot. The stems rot at the soil line or just below it. Plant where the soil and air drainage is good. Destroy diseased plants. Use benomyl to control this disease.
Wilt causes leaves of infected plants to yellow and the stems to collapse. Mildly infected corms may not show symptoms when dug but may rot in storage. The disease is caused by Fusarium orthoceras and may be controlled with benomyl.
Smut causes blistering, shredding and dying of stem and leaf tissue. No chemical control is listed.
Leaf and flower spot causes oval, tan to dark brown spots on the leaves and stems. Florets on heavily infected do not open. The disease is caused by Curvularia trifolii.
Several virus cause color breaks in the flowers. There is no chemical control