Box blight

Pippa Greenwood offers some sage advice against the troublesome box blight.

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If you grow box, you’ll be aware that there are a number of pests and pathogens that it may be attacked by, but there’s one problem which is causing more trouble than most; box blight. It’s  caused by the fungus Cylindrocladium buxicola but there is another type of box blight caused by the Volutella fungus but this is nothing like as damaging.

Symptoms of box blight

Whether you’ve got just a single bit of box topiary or you’ve created a hedge or parterre using box, the appearance of box blight disease can be devastating!

So what does it look like? Keep a close look out for blackish streaks on the young stems, often combined with dieback, leaf browning and death followed by dramatic leaf drop and the appearance of completely bare stems.

If the weather is wet or damp then take a close look beneath infected leaves and you’re also likely to see white spore masses. (If these spores are a distinct pink colour, then you’ve got the Volutella box blight).

So what can you do?

There are a few things you can do to keep your plants free from the dreaded box blight.

  • Box blight fungus thrives in damp conditions. Sadly we can’t change the weather but you can do anything possible to reduce humidity around the stems.
  • If you need to water your box, never do so from above, but always directly at the base. Careful use of secateurs can help – cut back other plants which are growing too close and avoid pruning and shaping your box too much.
  • If you prune and clip really frequently you’ll get a really good, close structure BUT sadly this is also a haven for the blight fungus which loves the closely packed stems and foliage – it also helps if you try to prune so that the top of the hedge or topiary is slightly rounded rather than flat as this too will help to reduce moisture build up
  • If you do get an outbreak of box blight the best thing to do is to dig up and bin or burn the badly infected plants and swiftly prune back hard any showing early signs of attack. It is also worth removing any dead leaves lodged within the plant as these may harbour the infection.
  • There are fungicides available, which may also help but, as ever, prevention and avoidance are your best courses of action!

 Damage limitation

So how can you minimise the chances of the disease appearing in your garden?

  • If you know your own box plants are perfectly healthy then rather than buying in new plants from a garden centre or nursery, why not raise your own from cuttings? Plants raised from healthy plants will be free of box blight and safe to plant in your garden.
  • The problem is that some commercial growers may use a different range of fungicides to those available to us and it may just be that the plants you’ve just bought have been sprayed with a fungicide that keeps them looking healthy and good – a treatment which supresses the fungus rather than actually killing it.
  • There is no way of telling when you buy plants, but if you then keep them in isolation (a sort of quarantine really!) for three weeks before you plant them, the effects of this treatment will have worn off and you’ll see if the plants are free of box blight or not.
  • It goes without saying that you should always check any new plants you bring in any way and only ever choose seemingly healthy plants.
Pippa Greenwood

About Pippa Greenwood

Pippa’s gardening passions include grow your own and the things gardeners hate most – pests and diseases! She gives many gardening talks and worked for the RHS for years, spent 13 years as a presenter on BBC Gardeners’ World and since 1995 has been a regular panellist on BBC Radio 4’s Gardeners’ Question Time. She was also the gardening advisor for the murder-mystery series, Rosemary & Thyme. Vist Pippa’s website www.pippagreenwood.com for gorgeous vegetable plants with advice from Pippa, pest controls and more
@PippaGreenwood
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