or black spots of variable size; as they expand,
lesions may be surrounded with a yellow halo,
and lesions centers may show sooty black,
concentric rings resulting from spore production.
Symptoms usually show first on lower, older
leaves. Lesions on flower stalks and pods are
typically elongated compared to the rounder
lesions that occur on leaves; infections on flower
stalks also may allow bacterial soft rot to enter the
stem, causing it to die prior to seed formation.
Diseased pods may be distorted and dry
prematurely, or be prone to shattering. Seeds in
diseased pods may not form, or may become
shriveled or blemished. Seedborne Alternaria can
occur as mycelium growing under the seed coat,
or as spores on the surface of the seed. Removal
of infected leaves may slow progression of the
disease. Burying crop debris is important as the
pathogen overwinters on exposed plant tissue. Hot
water treatment of seed can be an effective seed
treatment.