Corn Stalk Rots
Compliments of
Agronomy Services Department
Corn stalk rots are some of the most destructive diseases
of corn. They are prompted by environmental factors and are usually noticed late in the
growing season at early kernel set.
Stalk rots have several symptoms in common, and other
symptoms that are related to specific fungi. Most of the stalk rots cause a deterioration
of the pith tissue. The interior of the stalk takes on a shredded appearance and becomes
discolored. This discoloration may be brown or some other color depending on the pathogen.
The discoloration usually starts at the nodes, and rotted stalks can be easily crushed
when pinched. If the pith deterioration is the only symptom, it may go unnoticed.
Some symptoms are more obvious than signs of internal pith
damage, and plants die before the grain is mature. The tops of plants die back, turning
brown, gray, or purple, with a frosted appearance. In some cases the stalk surface becomes
discolored and lodging develops.
Here are common stalk rots with brief symptoms and causal
conditions:
- Anthracnose
Symptoms: Narrow oval lesions on
surface of lower stalk after tasseling. Lesions become tan, red, brown, and finally black.
Stalk interior turns brown to black and disintegrates. Lodging starts rather high up on
the stalks of affected plants. Die-off from the top down follows the appearance of stalk
rot symptoms.
Favorable conditions: Reduced
tillage, continuous corn planting, warm and wet conditions.
- Diplodia
Symptoms: Stalks break between
their nodes. Stalk interior is shredded with no internal discoloration. The lower stalks
are soft and easily crushed; lodging may occur.
Favorable conditions: Dry
conditions early in season followed by wet weather after silking. Danger increases with
continuous corn and residue on top of the soil surface.
- Fusarium
Symptoms: Lower internodes become
tan to dark brown. Lower internodes on the stalk interior are shredded and are brown,
pink, or salmon colored; stalk lodging may result.
Favorable conditions: Dry early
season, followed by wet conditions after silking; planting corn on corn more prevalent,
with residue on the surface.
- Gibberella
Symptoms: Pink to red inside
stalk, mostly pink at the nodes.
Favorable conditions: Corn
residue on top of soil; planting corn following wheat that had wheat scab. Occurs under
wet, cool conditions during and after pollination.
Management
Choose hybrids that have good stalks and tolerance to stalk
rots, especially continuous corn hybrids that specifically incorporate these features.
Balanced fertility and balanced soil tests seem to offer more protection to stalk rots.
Avoid excessive levels of nitrogen and low potash. Crop rotation tends to reduce the odds
of stalk rot fungi development.
For further discussion on stalk rot in corn refer to Iowa State
University Corn Disease web page.
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