The fungus can attack flax plants at any stage of growth. In the seedling stage, roots are ashen-gray in color and the small plants wilt and die. In older plants, leaves turn yellow at the tip first, turning completely yellow later on. The disease is seed and soil-borne, and affects plants mostly when temperatures are high. Since flax in Texas is grown in the winter, the disease has not caused serious problems.
Most common varieties are resistant.
Several fungi are involved in the complex disease. The fungi invade the capsule, turning the pod black and causing discoloration and rotting of grain. The disease is enhanced by insect damage and humid, wet conditions. Some varieties are more resistant to the disease because of the structural shape of the pod, which deters the entrance of organisms. Zinc deficient plants show death of the terminal bud, profuse tillering and necrosis of the leaves.