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Southern
Corn Leaf Blight (Bipolaris maydis)
is a member of the ascomycetes, or sac fungi, family. Mycelium and spores can
overwinter in soil and crop debris. Spores are blown by wind or in water
droplets onto the surface of leaves, and after they have germinated, they enter
the plant through the stomata. The fungus produces a toxin that and destroys the plants ability to capture energy from metabolism.
Under optimal conditions (20-30°C and moist weather), the
fungus can complete its life cycle in 2-3 days,
The
exact symptoms depend upon the race of the fungus and the strain of corn
affected. As a general rule, tan lesions are seen on leaves with the number and
size depending upon the fungal race and the strain of corn. In the worst case
the lesions are numerous and can be several centimeters long and have dark red
or purple edges. Ear and cob rot mat occur when kernels become infected with
black masses of conidia (asexual spores).
Stalks may also be damaged. The genetic basis of susceptibility to leaf blight
is well known and plants resistant to it are widely available and constitute the
first line of defense. If necessary, a large number of fungicides
are approved for use.
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