During rainy periods, the spots may merge to involve the whole leaf. Remove and destroy spotted leaves early in the growing season. Remove and destroy the tops in fall. Bacterial soft rot enters plants through wounds, often those caused by the iris borer. Rotting rhizomes have a foul odor.
Infected leaves have a water-soaked appearance.
Foliage may yellow and die back, and the plant may die if disease progresses. Wet, heavy soil and moist shade help promote this smelly disease. Discourage bacterial soft rot by planting irises in a well-drained soil and avoid crowded conditions. In the fall, remove and destroy dead leaves and plant residue in the iris bed. If you experience a severe outbreak, dig up the rhizomes in late summer.