Leaf spot causes irregular small brown spots with yellowish margins on the leaves. Several fungi can cause leaf spots. Cut off infected foliage and avoid wetting the leaves.
Fusarium leaf spot causes round, slightly raised, reddish brown lesions. These will be surrounded by a yellow halo.
Shrunken, straw colored areas is a symptom of tip blight. The disease begins on the lower leaves which may be killed. Center leaves are dead only at the tips. Cut off and destroy infected leaves.