Diseases of Winterberry Holly Plants
Winterberry holly (Ilex verticillata) is a deciduous plant that will brighten up any winter landscape with its masses of glossy, bright red berries. Also known as Black Alder, the shrub's branches, laden with berries well into the winter, are often used for decoration during the holiday season. It is found primarily in the eastern half of the United States.
The first symptom of this disease is the appearance of brown or tan spots on the leaves of the holly plant. Anthracnose is a fungal disease, and as it progresses, the spores of the fungus will appear on the inside of the spots as a bright pinkish or orange mass. A fungicide should be sprayed on the plant starting as soon as the spots are noticed and re-applied every two weeks until there are no more symptoms. Anthracnose, like all leaf-spot diseases, is most common when the spring weather has been unusually wet, warm and humid. If not treated, the leaves will quickly wilt and drop off the holly plant.
Pythium and Phytophthora Root Rot
Pythium and Phytophthora Root Rot are two common types of fungi that attack the roots of otherwise healthy Winterberry holly shrubs. Pythium usually occurs in container-planted holly bushes, while Phytophthora is more commonly seen attacking Winterberry holly shrubs in the landscape. The cause of these and other root rots is overly moist soil. Standing water can contribute to the proliferation of fungus growth, which attack the tissues of the roots. Make sure your holly bush is planted in well-draining soil, and watch for the common symptoms of root rot, such as yellowing leaves, early leaf drop (before fall) and twigs that are dying. If you suspect your Winterberry holly has Pythium or Phytophthora root rot, drench the soil around the plant with a fungicide.
Botryosphaeria canker (sometimes shortened to Bot canker) usually only affects Winterberry holly plants that have been stressed due to extreme climate conditions, transplanting, or another disease. This fungus affects the wood of the plant, growing under the bark and creating diseased, discolored areas of bark, or cankers. The cankers encircle or girdle the twigs, cutting them off from the rest of the plant and causing them to die. The leaves of the Winterberry holly will turn yellow and fall off prematurely, and the branches will begin to die back (die from the outer tips). Fungicide is not effective, so the best course of action is to prune away infected twigs and branches as soon as you notice them, preventing the spread of the disease.