Pests and diseases

 

Good breeding has developed new varieties of Helleborus that make them easy to care for in the garden. They are resistant to most pests and diseases. (see Helleborus Gold Collection) There are few remaining threats, and they are described below.

Aphids are probably the biggest pest. Primarily, they attack the new leaves. Other uninvited guests such as snails can sneak up in moist summers. There are snail repellants in garden centers or one can use the ever-popular “beer trap”.Furthermore a stinging nettle-slurry can be used to prevent that aphids colonize the plant.

In a cold winter mice can sometimes eat the new buds of the plants. The neighbour´s cat can help to minimize this problem.

Root nematodes, which are not visible with the naked eye, can be a problem. Should the plant exhibit stunted growth while it is getting good food and nutrients, this might be the cause. The nematodes suck on the roots of the plant, preventing food and water to the leaves of the plant. It is very difficult to attack these insects. Plants showing these symptoms should probably be dug from the garden and disposed of properly so that the nematodes do not increase.

Western flower thrips can attack the flowers. This generally would occur in the autumn. If there is a gnarly, deformed growing tip on new leaves this could also be the cause. At the first frost, thrips will be eradicated.

Fungal diseases are more difficult to the plant than pest damage because the appearance of the plant can be influenced negatively and/or the entire plant could perish.

Coniotyrium hellebori’ is the most famous fungus to attack Helleborus, it causes the Black-Spot disease. As the name suggests, this fungus creates black spots on the leaf edges. At the first signs of this disease you should start a control program. All the affected leaves should be cut off and thrown away so the fungus will not spread. Spray control programs with fungicides can be effective in controlling the disease. Watch closely for spread of the fungus once observed for repeat treatments. Causes of the disease can be a low pH and a location in the garden with too much moisture.

The symptoms of the Black Spot are similar to those of the Black Death disease, which is recently reported from England. It is probably a virus, which creates black spots and black streaks on all parts of the attacked plant. These plants must be destroyed because there is no cure for the virus. One of the few preventative measures one can take is to keep pest infestations to a minimum as they transmit the disease.

In the spring healthy leaf stalks can be attacked by a rhizome and stalk decay. The stalks lie on the ground and have brown or black areas at the base of the stalk. Several fungi can be the cause of these symptoms: e.g. Pythium, Phytophtora or Rhizoctonia. Treatment for these fungi is difficult. It is important to plant in soil that is well drained and does not hold moisture.

These were the pests and diseases which can occur at Helleborus under bad conditions. If other “visitors” or fungi lose their way on your Helleborus, you can get information in a specific shop, or you can use our discussion forum.