Boxwood Health Care

Common Pests of Boxwood

Monitor closely for insect pests and call us if problems arise.

• Mites: Pale speckles on leaves, beginning on the undersides. This is more of a problem when boxwood is planted in areas that get too much sun. Spray with horticultural oil.
• Leaf miners: Light-colored tracks visible on leaves. Prune off any new growth with tracks when first seen in early spring and spray with spinosad (Captain Jack’s Dead Bug Brew).
• Psyllids: Cupping of leaves. Prune out the damaged areas and spray horticultural oil or soap when new growth appears.
• Leaf miners and psyllids: Can also be prevented with a soil drench of systemic insecticide applied in spring before new growth is visible.

Common Diseases of Boxwood

• Phytopthora: Initially, individual branches turn dull and light green, then tan. This can spread rapidly and kill the whole shrub. It is often a problem in compacted or waterlogged soils. Regular soil drenches of systemic fungicide may hold the disease at bay, but the plant usually succumbs eventually. Any boxwood subsequently replanted where one died of phytopthora will likely also succumb.
• Volutella boxwood blight: Branches show new growth late or not at all, then parts of branches turn light green to tan; powdery spores may be visible on undersides of leaves. Prune out affected areas. Volutella is controlled by proper thinning to allow good air circulation.
• Nematodes: Plants bronze, become stunted, and generally lose vigor. Nematodes are endemic and can only be controlled by good cultural practices (pH management is very important) and keeping plants healthy and strong.
• Boxwood decline: A poorly understood complex of reduced vigor, defoliation, and eventual death, possibly involving a combination of several of the aforementioned diseases and poor planting environment. Again, cultural practices and planting environment have the most effect on prevention. American and Korean boxwood seem less susceptible.
• Boxwood blight (Emerging pathogen): Initial symptoms of boxwood blight include circular, tan leaf spots with a dark purple or brown border. Leaf spots may or may not have yellow to reddish halos surrounding the spot. Black stem lesions or blackening of the stems is often seen. Infected leaves become tan and drop from the stems in sections, with defoliation happening rapidly. The speed of defoliation is one characteristic that indicates boxwood blight rather than another boxwood disease. Non-curable, remove affected plants and do not replace with boxwood. If seen, consider the entire property infected.