Diseases in Gladiolus Bulbs

Brown Rot

• Brown rot, caused by Fusarium oxysporum, is a common type of rot that affects gladiolus bulbs. Symptoms of infection in the bulbs consist of brown to black spots near the base, shriveling of tissue and visible mold growth, according to the University of Wisconsin Extension. Infected bulbs will not sprout in the case of a severe infection. Mildly infected corms will sprout, but with yellowing of the leaf tips and poor growth. Fusarium favors nitrate rich fertilizers for growth and infection. Use fertilizers sparingly to prevent brown rot. Chemical fungicides are an effective method of control in the case of severe infections.

Vascular Rot

• Vascular rot, caused by Fusarium oxysporum, is a disease of gladiolus bulbs. The same fungus that causes brown rot also causes vascular rot, but occurs less frequently, according to the University of Wisconsin Extension. Symptoms of vascular rot consist of dark fungal growth in the core of the bulb and brown spots on the exterior. Because symptoms occur in the vascular section of the bulb, exterior symptoms do not occur until the rotting is extensive. Cultural control of the disease is similar to brown rot and consists of using fertilizer sparingly, planting disease free bulbs and testing soil for Fusarium fungi. University-based and private labs test can test soil for Fusarium spores. Apply chemical fungicides to infected soil before planting to prevent infection.

Stromatinia Corm Dry Rot

• Stromatinia corm dry rot, caused by Stromatinia gladioli, is a soil-borne fungal disease of gladiolus bulbs. Symptoms of infection consist of leaf discoloration, leaf death, red to brown lesions on the bulbs and black fungal growth in the bulbs core. The fungus favors cool and wet weather conditions for growth, and overwinters in infected plants. Do not continue to plant gladiolus bulbs in infected soil because continuous infections will occur from the soil-borne fungus, according to the University of Minnesota Extension. Treating soil with fungicides before planting and destroying infected corms is an effective method for controlling Stromatinia corm dry rot.