No known vector.

Sclerophthora rayssiae var. zeae may sporulate on either side of the lesions and appear downy or woolly. Sporangia disappear as the lesions become necrotic. Oospores occur only in necrotic tissue, in the mesophyll, or beneath the stomata, but not in vascular tissue.

Pathogen causes leaf lesions only (Putnam, 2007). Initially, lesions develop on the leaves as narrow, chlorotic or yellowish stripes, similar to other downy mildews, but only 3-7 mm wide. They have well-defined margins and are delimited by the veins. The stripes later become reddish to purple in some corn genotypes. Lateral development of lesions causes severe striping and blotching. The disease may first be noticed on the lower leaves, which will show the greatest degree of striping; as a result they appear pale-brown and burnt, and severely affected leaves may be shed prematurely.

Seed development may be suppressed, seed may be smaller in size, and the plant may die prematurely if blotching occurs prior to flowering.
Unlike other downy mildews, floral or vegetative parts are not malformed, and the leaves do not shred.

Morphological: condiophore structure and dimension and spore (conidia) shape and size.

S. rayssiae var. zeae may be confused with other Scleropthora species occurring on corn and other downy mildew genera, including Peronsclerospora and Sclerospora.

Other indigenous downy mildews and physiological conditions (fertility, weather, etc.) can cause similar symptoms.

Brown stripe downy mildew could be confused with two potentially destructive downy mildew diseases of corn already established in the United States: crazy top (Sclerophthora macrospora) and sorghum downy mildew (Peronsclerospora sorghi).

Sclerophthora rayssiae var. zeae is on the Select Agent List.