Inkberry (Ilex glabra), a type of holly bush, typically growing about 6 to 8 feet tall and 8 to 10 feet wide. The female plant produces black berrylike drupes, and both male and female have dark green, evergreen foliage. This plant grows in U.S. Department of Agriculture plant hardiness zones 4 through 9. Well cared-for inkberry plants within these zones rarely have many problems.
The leaf spot disease that affects inkberry is called anthracnose. Anthracnose appears as light tan to darker brown circular or irregular spots on the leaves. It spreads through spores in moist weather, which you can see with your naked eye as pinprick-sized pink dots in the leaf spots. To control, prune out diseased limbs and/or apply a fungicide containing thiophanate-methy or chlorothalonil until the disease is gone. To prevent anthracnose, avoid overhead watering.
Root rots can also affect the inkberry holly, especially Phytophthora and Thielaviopsis black root rot. They both cause yellowing of the leaves, early leaf drop, slow growth and, eventually, branch dieback, and occur most often with flooding and extreme heat. Fungicides cannot cure the holly plant of this disease but can stop the spread. Thiophanate-methyl will help with Thielaviopsis root rot and etridiazole and metalaxyl with Phytophthora. As the diseases cannot be cured, prevention by planting the inkberry in well-draining soil is your best bet.
Botryosphaeria canker affects weaker inkberry plants, usually following extremely high or low temperatures and drought. The canker causes similar symptoms to root rot, including yellowing of the leaves and dieback. The cankers appear as sunken or cracked patches of wood, and girdle the stems so nutrients cannot reach the leaves. Prune out diseased branches as you notice them and take better care of the holly, watering during drought and mulching to retain soil moisture.
Most pests don't bother inkberry, but some do. Aphids attack new growth and scale insects are sometimes a problem, but both can either be removed by hand or with a quick blast of water. The inkberry leaf miner can be a larger problem, creating ragged leaves. In small infestations, you can pick the leaves off the plant, while larger infestations may require pesticides. During droughts, spider mites can also appear.
Inkberry is susceptible to chlorosis, a yellowing of leaves caused by alkaline soil. This is one of the symptoms of some of the diseases that affect inkberry, so if you suspect canker or root rot, test the pH of your soil first. In cooler areas, the foliage may suffer from winter burn when temperatures drop below minus 15 degrees Fahrenheit.