Increased planting of the moderately resistant runner varieties has reduced the relative importance of web blotch. Symptoms Web blotch symptoms appear first on the upper leaf surface. Symptoms may either be a brown to bronze webbing or netlike discoloration of the leaf, o r roughly circular, dark brown spots or blotches having irregular, diffuse, and light brown margins. Webbing is the growth of fungal strands beneath the leaf cuticle. Under favorable environmental conditions, webbing may enlarge rapidly to cover the entire leaf.
Blotches are less developed and pale brown on the lower leaf surface.
Conditions that favor development of the webbing symptom over blotching are unknown. The regular border and bright yellow halo surrounding early leafspot lesions are conspicuously absent with web blotch. Defoliation may be severe when leaf lesions are extensive or numerous. Symptoms of web blotch showing typical large, irregularly shaped, brown blotches. The disease cycle of web blotch is not well defined.