The holly plant is part of a group of evergreen and deciduous trees and shrubs having ornamental foliage and producing brightly colored berries. The foliage and berries are used for decoration and are attractive to birds. While disease is not common in holly plants, there are several that may infect the plants. Following preventative measures will assist in lower the chance of the plants being infected.
Holly bushes and shrubs have foliage that is glossy in texture and prickly on the edges. The plants are dioecious, meaning there are separate plants for male and female. The females produce bright red berries only if a male plant is located nearby. The evergreen type of holly is hardier in nature and will grow in size from 6 to 40 feet in height.
The holly plant prefers locations that are full sun or light shade in a soil that drains well. Many varieties prefer a slightly acidic soil. Plant the bushes or trees at a spacing no less than 5 feet apart. The plant should be mulched at a depth of at least 2 inches and spread out to the point where the branches end.
Water holly during the summer months when there is less than 1 inch of rainfall per week. The plants require little pruning, however a spring pruning will promote berry production and prevent disease.
Common pests for holly plants are mites, scale and leaf miner. Spider mites attack the leaves and produce a web as they move about. An infestation will cause the leaves to spot and discolor as they attack foliage. Treat and prevent mites by applying insecticidal soap to the plants. Scale bugs are small, tan bugs with a scale or shell over their body. They infest the underside of leaves and at leaf joints. The bugs do not fly, requiring hand removal from the plants.
Placing sticky tape at the base of the plant prevents the bugs from crawling up the plant. Leaf miner is a larvae type bug that burrows in the leaves, leaving a yellow brown trail. Foliage infested with leaf miner must be destroyed. The remaining plant must be treated with foliar insecticide.
Holly plant diseases are commonly the fungal diseases tar spot and cankers. Tar spot produces yellow spots on the leaves which eventually turn into red brown or black colored spots. The leaves will eventually get holes and drop from the plant. Cankers are a fungus that infects the stems, causing indentations which eventually kill the branch.
Both fungal infections require that infected areas be removed and destroyed. Prune the plants to increase air circulation during wet conditions and prevent fungal infections.
Environmental problems with holly plants include scorch, purple blotch, or iron deficiencies. Holly scorch is a condition that occurs in late winter where temperature fluctuations cause the leaves to turn brown. Shading the plants during these conditions will prevent further damage. Purple blotch in the plants occur due to injury, drought conditions, or nutritional deficiencies.
When under these conditions, the plants produce purple colored spots on the leaves. Treating the condition requires evaluating the cause and changing the condition causing to reduce the problem. Iron deficiency in holly plants causes the foliage to turn yellow or pale in color. Treatment requires lowering the pH of the soil and applying a fertilizer with iron.