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Box blight

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last updated Apr 11, 2014
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Box blight. Image: RHS, Horticultural Science

Box blight is a fungal disease of box resulting in bare patches and dieback of box, especially in topiary and parterres.

What is box blight? Back to top

Box blight is a disease of box leaves and stems caused by two fungi, Cylindrocladium buxicola and Volutella buxi. The two are often found together.

This is a disease which largely affects Buxus spp. (box) in the UK, but can also affect other plants in the Buxaceae family.

Blight is just one of a number of problems box suffers from.

Symptoms Back to top

You may see the following symptoms:

  • Both fungi cause leaves to go brown and fall, leading to bare patches
  • C. buxicola, the more damaging of the two, also infects young stems causing black streaks and dieback
  • In wet conditions the spore masses of the fungi may be seen on the undersurfaces of infected leaves, white for C. buxicola and pink for V. buxi
© RHS

Cylindrocladium buxicola, the more damaging of the two box blights, infects young stems causing black streaks and dieback.

Control Back to top

Non-chemical control

Cultural control and hygiene

Hold any commercially sourced plants in isolation for at least three weeks to confirm they are free of infection before planting out. Commercial nurseries may use fungicides which suppress but do not kill the fungus and this isolation technique will allow time for any suppressed disease to become visible.

If the disease does break out, remove and destroy affected plants. If they are mature and highly valued, cut out all affected parts, clean up fallen leaves (including stripping and replacing surface topsoil to ensure complete removal) and treat with a fungicide.

Resistance

Unfortunately there is not known to be a resistant Buxus at present.

The host range of both fungi is not fully known, but C. buxicola attacks Buxus balearica, B. bodinieri, B. glomerata, B. harlandii, B. microphylla, B. macowanii, B. riparia, B. sinica and B. sempervirens. Other plants in the Buxaceae family are susceptible such as Pachysandra terminalis and Sarcococca species.

Choose alternative hedging and topiary plants

To be completely safe, choose an alternative hedge or topiary plant. The following all have small leaves and can be clipped into formal hedging styles:

Chemical control

There are no fungicides available to amateurs with specific recommendations for use against box blight. However, the fungicides difenoconazole (Westland Plant Rescue Fungus Control), myclobutanil (Bayer Garden Systhane Fungus Fighter and other products), tebuconazole (Bayer Garden Multirose Concentrate 2) and triticonazole (Scotts Fungus Clear Ultra) are labelled for control of other diseases on ornamentals and could therefore be used legally on box (at owner's risk) to try and control box blight. Research undertaken by the RHS has investigated myclobutanil and found it to be ineffective at controlling Cylindrocladium blight.

Download

Fungicides for gardeners (Adobe Acrobat pdf document outlining fungicides available to gardeners)

Biology Back to top

The fungi survive as resting structures or mycelium on fallen leaves for up to 6 years and produce spores when conditions are suitable. The spores are dispersed in water and probably by animals and birds. They may be spread in wind-blown rain, but are unlikely to travel long distances on the wind. As well as natural means of dispersal, these fungi have been spread widely by human activity, especially on infected plants from nurseries.

V. buxi requires wounds for infection and is associated with clipping. C. buxicola can infect unwounded plants and causes more serious damage.

V. buxi has long been known, but little studied. C. buxicola was first recognised in the UK in the mid 1990s and has also broken out in northern Europe and New Zealand, but its origin is unknown.

Both fungi can infect the very common Buxus sempervirens and several other species.

Further reading

RHS research into box blight

Quick facts

Common name Box blight
Scientific name Cylindrocladium buxicola and Volutella buxi
Plants affected Buxus spp. (Box)
Main symptoms Brown leaves and bare patches
Caused by Fungus
Timing All year round, most active in spring and autumn
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