Plants affected
Buxus sempervirens and other box species.
Symptoms
Symptoms depend on which fungus is responsible:
Photograph copyright T. Sandall - Blight symptoms on box span class="style1">Volutella: pinkish spores appear in wet weather on the undersides of leaves. The disease spreads in wet, humid conditions. It overwinters on fallen leaves, and produces spores in the spring, which infect leaves and twigs through clipping wounds and cracks.
Cylindrocladium: spots can be seen on the leaves, which develop into larger necrotic areas. The fungus also causes black streaks on the stems and branches. Patches of greyish fungus appear on the lower leaf surface. As the disease advances leaves are lost from the plant.
Cause
This disease is caused by two fungi, which may be present on the plant together.
Volutella is an established pathogen of box in UK.
A new species of Cylindrocladium (C. buxicola) has been recognised in the UK since the mid 1990s. It is a relatively new problem occuring on box plants. Cylindrocladium is currently being studied at Wisley to find out more about its origin and pathogenicity.
Non-chemical control
Hygiene measures are the most important method of control for this disease. Ensure that new plants are disease free before purchase to avoid introducing this problem into the garden. Prune all infected branches promptly and collect any debris from around the base of the plants.
Chemical control
No chemical control is available specifically for this disease. The fungicide penconazole (Scotts Fungus Clear) is approved for use on ornamentals and may give some control, based on laboratory studies at RHS Wisley.
