Box Blight

The Disease(s):

Box blight is a fast spreading fungal disease that kills topiary and hedges containing varieties of Buxus (known as ‘Box’) within a season.
‘Box blight’ is actually one, or a combination, of these two separate fungal diseases:

Cylindrocladium:
Usually starts as dark fungal spore
infection – leaves black spots or dark
bare twigs

Box Blight Cylindrocladium
Image rights: Wikimedia Commons License
             

Volutella:
Leaves turn brown and wither but stay
fixed to the plant


Box Blight Volutella
Image rights: Wikimedia Commons License

 

Fungal pathogens, or disease spores, can take only a matter of hours to infect leaves.
They are transferred from infected plants via water splashes but can live on leaf litter and dead plants for many weeks or months. (see Prevention).

Treatment:

  • There are a number of fungicides that have been trialed by growers in mainland Europe, with some success, in protecting against initial infection and some that attack the infection - but not all are approved for use on Amenity vegetation (Buxus).
  • Once a leaf or branch has died it cannot be brought back to life.
  • Signum is approved through an EAMU (Extension of Authorisation for Minor Uses).
  • Warm, wet spring is the worst time for the disease to spread
  • Dry periods are better to limit disease.

Prevention:
Prevention can be better than cure, but its no guarantee...

  • Collect fallen leaves from all plant species in the vicinity regularly and remove dead plants – then burn…do not compost.
  • Water during dry weather using drip tubes rather than spraying the foliage. Alternatively soak the soil once a week rather than sprinkling multiple times a week
  • Disinfect cutting equipment after every cut; secateurs, shears and hedgetrimmers– use Propellar or Jet 5 disinfectant.
  • A strong plant will resist the disease better in the first place. Fertilise using small amounts of fish, blood & bone or ideally a slow release fertiliser to avoid provoking a sudden flush of leggy growth that is weaker and more susceptible to spore infection.
  • Some varieties of Buxus seem to withstand infection better than others. Unfortunately the most popular variety Buxus sempervirens 'Suffruticosa' seems to be the most susceptible to disease.
  • Newly purchased plants (buxus or otherwise) should never be planted straight away near box to reduce the importation of infection. Keep new plants in ‘quarantine’ for a short period to observe any signs of disease developing.
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