Boxwood Shrub Disease

English and American boxwood are popular hedge shrubs. Both types of boxwood can be affected by fungal, stem and root diseases.

Volutella stem blighti is a fungus that affects boxwoods and is thought to be brought on after winter frost; the only cure for this disease is pruning affected areas. Before spring growth begins, stems turn orange or brown and then die back.

Macrophoma leaf spot appears on boxwood when it is affected with another disease. Characterized by dark splotches on dead leaves, Macrophoma leaf spot is a sign that something else is wrong with the shrub, probably a root disease.

Two major root diseases affecting boxwoods are phytophthora root rot and root-feeding nematodes. Plants affected with these diseases will show yellowing leaves. Root-feeding nematodes are parasites that can appear at any time, while phytophthora root rot primarily emerges after the plant experiences excess water at the roots.

English boxwood decline affects large English boxwood plants, commonly 20 years or older, and is likely brought on by drought conditions. Foliage turns yellow then progresses to straw colored.

Water English boxwood in hot, dry summers to prevent boxwood decline. Avoid planting English boxwood in soil where previous plants suffered boxwood decline. To prevent phytophthora root rot, plant in well-draining soil and use raised beds; applying a fungicide to cases you've caught early can help cure plants.