Symptoms
Flag smut symptoms become apparent during
the stem elongation and heading stages of growth.
Infected plants become increasing obvious during
the early stages of grain development. Infected plants
are deformed and often noticeably
shorter than healthy plants. The stunted plants are
often restricted to the lower third of the crop canopy.
The leaves of diseased plants are often twisted and
have long gray or black lesions that run parallel to the
leaf veins. As the plants mature, the lesions rupture and
release large numbers of black, powdery spores of the
fungus. Flag smut may infect all the tillers of a plant,
but in some cases, only a few tillers become diseased.
The heads of diseased tillers are poorly developed and
often will not emerge from the twisted flag leaves.
Heads that do emerge may have black-striped stems
and glumes. The infected tillers often produce no grain
Management
Fungicide seed treatments are the most effective
way to manage flag smut. There are many seed treatment fungicides labeled for control of flag smut and
many of the widely marketed fungicides should provide
excellent control of the disease. The genetic resistance
of wheat varieties grown in Kansas is unknown.
Crop rotations with nonhost crops such as
soybeans, sorghum, or corn provide time for the fungal
population to decline between wheat crops and lower
the risk of infection in subsequent years. It also may be
possible to reduce the risk of severe disease by avoiding
early planting conditions that place seed into warm
moist soils, which are known to favor infection by the
flag smut fungus.