The disease is favored by planting too deep, injuring the stem while planting, or by soluble salts injury. Rotting tissues usually have a disagreeable odor. The disease is favored by the use of soft, succulent cuttings and warm, damp conditions. In mid-season, Pythium fungi invade roots made vulnerable by water stress or excess soluble salts, causing discoloration and decay of feeder roots. Loss of root function produces yellowing, wilting, and possibly death of infected plants, especially under stressful growing conditions.
Diseased roots lead to stunting and poor growth of plants.
Botrytis may also cause a stem blight on cuttings and plants. The Botrytis fungus can colonize dead plant tissues and produce large numbers of spores. Disease control is best done through prevention using a program involving sanitation, cultural control, and chemical fungicides. Sanitation is important for control of any greenhouse crop disease, and poinsettia is no exception. Disease-causing fungi and bacteria survive in plant debris from the previous crop, and in soil and water left on floors, benches and equipment.