Diseased plants have lesions on their roots immediately below the ground line. These lesions enlarge to kill seedlings and weaken older plants. Flax plants with roots injured by Rhizoctonia solani appear to be considerably more susceptible to damage by cold weather and root rotting fungi. Use recommended seed and soil treatment fungicides. This is probably the most important disease of flax in Texas.
Lesions develop first on the cotyledons and later on the lower leaves of the seedling.
Lesions are usually circular and vary in color from greenish yellow to dark brown, depending upon age. Later, stem lesions develop, first as small elongated lesions which then enlarge and coalesce, extending around the stem as well as longitudinally. There is no evidence that the fungus oversummers in Texas, so it is likely that the disease is primarily seed-borne. Rotation and removal of straw or covering the straw with plowing helps reduce the inoculum. Use seed treatment and resistant varieties.