What is Box Blight and What Can I do About it?

If your box hedge has started to turn brown and the stems have begun to die back, chances are it’s suffering from box blight. Here we share all you need to know about this fungal disease that affects box plants, including how to keep the problem under control and restore your hedges to the lush green they once were.

Box blight (Cylindrocladium buxicola) is a fungal disease that affects the common box (Buxus) plant. It first came to light in Britain in the 1990s, and is worst in warm, humid conditions.

Box blight causes leaf browning and stem dieback. The plants turn straw-coloured and develop bare patches, which are especially noticeable on hedges and topiary. Box blight doesn’t actually kill the roots, but it does make the plants weak. It invades the tissues of the plant, interfering with water transport, and consequently killing the cells.

Whilst recovery from box blight is possible, it takes a lot of perseverance to keep the problem under control, and it’s a whole lot easier if you catch it early and start treating it straight away.

How to identify box blight?

It’s easy to confuse the symptoms of box blight with those of the box tree caterpillar, so be sure to closely examine your box plants before you make the assumption.

If you discover dark lesions on the leaves which subsequently turn brown and drop to leave bare stems; you spot black streaks and dieback of young stems, and/or you see white spores on the undersides of infected leaves, then you are dealing with box blight.

If the spores are pink, then you are more likely dealing with Volutella blight, which is also common in box plants, but less serious.

How does box blight spread?

The disease is likely spread from plant to plant by splashing water, either from rain or watering.

The spores are sticky, so may also be carried by birds and animals, or even by gardeners on tools, shoes or clothing. Moving infected plants or soil containing infected remains such as fallen leaves can also spread the disease.

How to treat box blight?

Box blight needs to be treated immediately you spot signs of infection as once it takes hold, it can be very difficult to get the better of.

Cut out the infected area and a good sized area around it. Be sure to do this in dry conditions, as if it’s wet you will risk further spreading the disease. If you are not opposed to using fungicides, do so before and after cutting back.

If cutting out infected areas isn’t sufficient, you can try cutting the plant back by half or a third. This will of course only work on hedging. It will get rid of the affected areas and allow more light and air to circulate to help the healthy parts of the plant recover. You may also choose to cut the plants right down to their stumps, or it may be necessary to remove an affected plant altogether.

It’s vital that you make sure your pruning tools are sharp and disinfected both before and after use. Try not to use power tools, as these can crush the leaves making them more prone to infection.

Always carefully dispose of infected material to stop box blight spreading around the garden. Never put diseased cuttings or leaves into your compost bin.

Wash your hands thoroughly and change your shoes and clothing once you’re done before moving on to any other gardening tasks.

How to prevent box blight?

It’s important to check your box hedges or topiary on a regular basis for signs of infection, always remembering that it’s much easier to treat box blight if it’s caught early.

Stick to pruning box plants just once a year, and always in dry weather. This will reduce the density of the plant so that air can circulate more freely. Pruning once a year will also reduce the risk of infection spreading.

Be sure to prune only in dry weather, and early in the season so there is optimum time for the growth to ripen, reducing the risk of frost damage that allows fungus spores to get into the plant.

Try to plant your box in relative isolation, away from other plants so that they have plenty of air circulation. Avoid dark, damp locations. Bright, open spots are a much better option.

Always make sure you pick up any fallen leaves, and be scrupulous when it comes to disinfecting your pruning tools.

You can buy organic tonics that help to prevent outbreaks. These need to be applied regularly throughout the growing season, which runs from April to October.

Never water box plants anywhere other than around the base of the plant, as the disease thrives in humid conditions and is spread through water.

Avoid fertilisers that are high in nitrogen as they prompt soft, sappy growth that tends to be more prone to infection. Opt instead for seaweed or bone meal feeds and apply once a year in the spring.

Make sure you buy your Buxus plants from a well-regarded supplier, and keep them quarantined for at least one month before planting to make sure they are free from blight. If you can, buy a blight resistant variety, such as ‘Faulkner’.

Finally, if your box plants have suffered an infection, the advice is not to replant for six years, as the spores can linger in the garden for some time.

Looking for professional help with your box or other hedges?

Whether you need help controlling a disease such as box blight, or you are looking for professional hedge trimming or hedge removal services, TH Trees Ltd can help.

Our extensive experience and professional qualifications allow us to identify and treat a range of common tree and plant diseases. So if you are worried about any tree or hedge on your land, please do get in touch.

4 Easy Maintenance Trees to Brighten Your Garden

How to Care for Your Trees in Winter