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.
Plants are small and unthrifty with reduced yields.
Another condition, late season decline, results in the wilting of plants brought about by drought stress during the flowering stage.