Hellebore Black Death Info
Hellebore Black Death is a serious disease that was first observed by hellebore growers in the early 1990’s. Since this disease is relatively new and its symptoms are similar to other hellebore illnesses, plant pathologists are still studying its exact cause. However, it is believed by most to be caused by a Carlavirus — tentatively called Helleborus net necrosis virus or HeNNV. It is also believed that the virus is spread by aphids and/or whiteflies. These insects spread the disease by feeding on an infected plant, then moving to another plant which they infect as they feed from viral pathogens left on their mouthparts from previous plants. Signs and symptoms of Hellebore Black Death, at first, may be very similar to Hellebore Mosaic Virus, but it has been determined that they are two separate viral diseases. Like mosaic virus, symptoms of Black Death may first show up as light colored, chlorotic veining on the foliage of hellebore plants. However, this light colored veining will quickly turn black. Other symptoms include black rings or spots on petioles and bracts, black lines and streaks on stems and flowers, distorted or stunted leaves, and die back of plants. These symptoms are most common on the new foliage of mature plants in late winter through summer. Symptoms may develop gradually or escalate very quickly, killing the plants in just a few weeks.
How to Manage Hellebores with Black Death
Hellebore Black Death mostly affects hellebore hybrids, such as Helleborus x hybridus. It is not commonly found on the species Helleborus nigra or Helleborus argutifolius. There is no treatment for hellebores with Black Death. Infected plants should be dug up and destroyed immediately. Aphid control and treatment may reduce the spread of the disease. Purchasing healthy specimens may also help.
