Southern Blight (fungus – Sclerotium rolfsii): Plants affected by the southern blight fungus begin to wilt, leaves turn crisp brown and the entire plant dies. Cutting into the stem shows a brown discoloration in the vascular tissue. A white mold growth will be apparent on the stem about the soil line. As the white mold ages, white-to-brown small, bead-like structures (sclerotia) form. These are overwintering structures of the fungus. Rotation, deep burial of residue, and planting on a raised bed will aid in reducing southern blight.
Top Necrosis(virus): Young leaves are curled, shed from the plant, and the terminal end of the stalk dies and turns black.
Bacterial Blight (bacterium – Xanthomonas cymopsidis): This is a seed-borne disease that causes loss of plants from seedling stage to maturity. Large angular lesions develop on the leaves which cause defoliation and black streaks in the stem.
Other diseases: Fusarium wilt, the cotton root rot fungus, curly top virus, and root knot nematodes attack guar plants.