Volutella Blight: Symptoms of this fungal disease become visible in the spring with poor growth on individual shoots or the entire plant. Affected twigs and leaves turn from green to red, then brown and finally to tan color. Fungi usually develop underneath the affected leaves and stem parts. In those sites waxy, salmon pink colored fruiting bodies can be observed using a hand lens. Affected leaves turn upward and lie close to the stem. Young boxwood leaves are more susceptible to the disease than old leaves. Black streaks on petioles and stems are another symptom that is observed in some of the infected plants. In later stages the bark becomes loose and discolored. In wet conditions stunted growth of the plants and leaf drop can be observed due to Volutella blight disease. Boxwood plants become more susceptible to this pathogen when subjected to wounds or winter injury.

Fallen leaves and diseased leaves should be removed from plant surroundings. Plants should be thinned to improve the light penetration and air circulation. Diseased branches should be pruned out a few inches below the transition zone (area between dead stem tissue and healthy green tissue). Pruning equipment should be sanitized once they are used to prune an infected plant. Irrigation should be well planned to minimize drought stress but avoid high humidity for long periods. Plants should be grown in well-drained soil or media with pH between 6.8-7.5. Light shade (20%) could be used to reduce injuries from seasonal extremes. Fungicide application should start in spring and continue until late spring. Even during the rainy seasons in fall, fungicides need to be sprayed to protect late summer growth. Fall fungicide application may be necessary to protect late summer growth if the weather is rainy. Thorough spray coverage of the branches and foliage is critical for effective disease management.

Root Rot:

Phytophthora spp. and Ganoderma lucidum

The fungi, Phytophthora spp. and Ganoderma lucidum, cause a root rot in both English boxwood and American boxwood. Symptoms include poor growth, loss of healthy foliage color (leaves eventually turn light yellow), upward turning and inward rolling of leaf margins, dark brown discolored wood at the base of the stem for 2 or 3 inches above the soil line and loosening and separation of the dead lower bark. As a result of the fungal infection, the root system is reduced and dark brown.

Although there are no chemical cures for these diseases they can be prevented by proper planting. Avoid planting boxwoods in poorly drained compacted soils or in low areas where water collects. Also avoid placing boxwoods near downspouts. Construction of raised beds or grade changes may be needed to ensure proper drainage. Root diseases on older established plants can result from changes in water drainage patterns.

Read more about root rot issues here on this website, or in UT Publication 289, 'Phytopthora Root Rot', found here.