Control Plant Diseases
For Better Farming And Better Living

Mimeo BP 1-10
March, 1958

GLADIOLA CORM DISEASES

Diseases of gladiolus corns, are just as important as leaf and flower
diseases. They often are responsible for failure of plants to thrive and
produce satisfactory blooms. The more important bulb or corn diseases of
gladiolus in Indiana are described below,

Fusarium Wilt and Corm Rot
Fusarium wilt is probably the most common gladiolus disease in Indiana
and is often referred to as yellows. While there are several varieties of
gladiolus resistant to this disease, no variety is entirely immune. Corns
from plants infected with fusarium will show a brown discoloration when the
corm is cut in half. The brown discoloration begins at the basal scar and
spreads upwards into the core, outward to the nodes and often extends into
the base of the leaves. When fusarium-infected corms are planted, many of
them will rot in the ground without sprouting. Others may produce sickly,
yellowed plants but none of them will produce satisfactory plants in the
garden, Fusarium corm rot will continue to develop in storage.

Bacterial Scab
Bacterial scab is frequently a destructive foliage disease which will
spread in wet weather to the bulbs. Lesions of bacterial scab will fre-
quently appear on the corm husks as definitely outlined, pale yellow, water
soaked circular spots. The scab lesions quickly turn light to dark brown
in color and finally become shallow depressions surrounded by a definite
raised margin. Another destructive symptom of bacterial scab on gladiolus
corms is the production of gummy exudations that cause the husks to become
glued to the corm. The individual scab lesions on gladiolus corms may be
relatively small or may attain a size up to one-quarter inch in diameter.
Scab lesions do not extend very far into the flesh of the corm and may be
readily removed leaving a saucer-shaped depression that will still harbor
the bacterial scab organism Pseudomonas marginatum,

Sclerotinia Dry Rot
Gladiolus corms, affected with this trouble, characteristically have
many small lesions ranging in size from mere dots to large areas approximate-
ly one-half inch in diameter. Typical dry rot lesions are roughly circular
in outline and appear first as small, reddish-brown spots, usually on the
side and lower half of the corm but not infrequently on the upper half as
well. As the dry rot lesions increase in size, the centers become sunken
and the color changes to black with a noticeable slightly raised margin. In
most cases, gladiolus corms infected with dry rot will mummify in storage.
Dry rot is caused by the fungus Sclerotinia gladioli and infected corms can

PURDUE UNIVERSITY Agricultural Extension Service, Lafayette, Indiana
Department of Botany and Plant Pathology, Life Science Building