Elderberries are large shrubs grown for their decorative appearance and slightly sweet and tart berries, which are often used in jams, jellies and beverages. Elderberry plants prefer moist, fertile soils, can grow in a range of soil conditions and are usually free from disease. There are some diseases that do affect elderberries that should be addressed when encountered.
Many different fungi can attack elderberries, producing a canker--a soft, dead spot on the branches and stems of the plant. If left untreated, the canker can completely girdle the branch, killing it. If the trunk is affected, it can kill the entire plant. Cold injury, drought and excessively wet conditions can produce stresses that can trigger an infection.
Affected branches of the tree should be removed below the infection site and destroyed. It is important to follow proper hygienic practices, such as disinfecting pruning tools between cuts. Powdery mildew fungus will also attack elderberries, although it is not a serious problem. Infected leaves can be removed in the fall.
Tomato ringspot virus
Originally discovered in tomato plants, this viral disease also affects elderberries and is spread by nematodes that carry the disease and infect the plant when they feed on it or infected pollen that is transferred by insect pollinators from a diseased plant to a disease-free plant. When an elderberry plant is infected, it gradually weakens and becomes debilitated. It may take several years for the disease to kill the plant. In the meantime, the fruit production of the plant is adversely affected, which can significantly reduce crop yields.
There is no cure for this tomato ringspot virus. Prevention is the only method of control. Wild elderberry plants in the area that may harbor the disease should be destroyed. Elderberry plants should be purchased from trusted growers that will guarantee the plants sold are disease-free. Infected plants should be removed and destroyed as soon as the disease is discovered.
Verticillium wilt affects elderberry plants, caused by the fungus Verticillium dahliae. The leaves become yellow or appear burnt and the plant wilts, sometimes only on one side. Poor growth can occur, branches may die back and the plant may die completely. The disease is spread through wounds or natural openings in the root system.
To control the disease, the soil prepared for planting elderberries can be fumigated with a fungicide prior to planting. Fungicides are ineffective for treating this disease, once it is established. Infected plants should be removed and destroyed immediately upon discovering the disease to prevent its spread.