Black Rot in Helleborus

Identification

• Black rot or black spot in helleborus is caused by Coniothyrium hellebori, a fungus that thrives and spreads during wet spring and fall weather. Plants that remain wet for extended periods are prone to the malady.

Damage

• Disease starts with dark brown to black spots on both sides of foliage. The spots spread gradually to flowers and, with time, merge and create large patches. Black, fungal fruiting bodies appear within the spots. Foliage starts to wilt and die. Cankers appear on stems and cause death, and flower buds wilt before blooming.

Management

• Preventative measures are best to control the disease, as there are no chemical options. Avoid areas of poor ventilation and excessive humidity. Do not use overhead irrigation systems, as extended periods of moisture promotes fungal development. Prune and remove all affected plant areas.