While many people think of holly as a holiday decoration, the holly bush makes an interesting year round addition to the garden. Hollies come in many shapes, sizes and colors. Many have variegated leaves, while some have the more traditional deep green foliage and bright red berries. Holly bushes can be prone to disease however, so be sure to keep your eyes open for the start of any problems.
Purple blotch is characterized by purplish spots on the leaves. This disease is usually brought on by drought, but can also be caused by injuries to the plant or by a lack of nutrients such as manganese, iron and sulfur. Applying a 4-6-4 fertilizer at the first sign of the problem can help to alleviate the problem. Prune off any affected foliage and bag or burn it to keep the disease from spreading. To protect your holly shrub and to prevent purple blotch from infecting it, apply a 4-6-4 fertilizer in the fall and again in the spring.
Chlorosis is caused by iron deficiency. Bushes affected by chlorosis will have very pale green to yellow leaves that have dark green veins. If this happens, immediately apply an iron additive with 55 percent sulfur and 22 percent iron in addition to other soil amendments, or use a spray containing iron chelate. This should help the leaves regain their green color. If that alone does not solve the problem, have your soil tested for pH levels at your local university extension service and follow the extension's advice.
Holly scorch, a condition where the bush's leaves turn brown around the edges, is usually caused by extreme winter temperature fluctuations. There is little you can do to prevent this other than to plant your holly bush in a sheltered spot if you live in a northern climate above USDA Plant Hardiness Zone 6. Different varieties of holly bushes have different temperature tolerances. Be sure to choose a holly that is suited for your climate. If your holly does get scorch, prune off the leaves to help restore the appearance of the shrub.
Holly bush canker shows up on the shrub's stems as a dark depressed spot. Cankers are usually caused by one of a number of fungal infections. If you see evidence of this disease, immediately prune off any affected wood and remove it from the garden area, as this disease can spread rapidly, killing the plant. Spray with a wide-spectrum fungicide to prevent reinfection. Prune plants to allow for more air circulation.
Holly tar spot is caused by a fungus. This disease causes black or yellow spots to form on the bush's leaves, usually beginning with the bottom of the plant and spreading to the top. The infected leaves will turn yellow and eventually fall off. To prevent tar spot, do not water your holly bush early in the morning or late at night when the water will sit on the leaves. Keep an eye out for early signs and treat immediately with a fungicide. Tar spot is not fatal to the bush but it can cause the entire shrub to lose its leaves.