Box blight was first recognised in the mid 1990’s and has now become a real problem in many gardens all over the UK, especially with the warm and damp weather.
If you suspect box blight in your garden then please feel free to contact me for advice or to discuss our fungicide treatments to help prevent the disease.
So what is Box Blight?
Box blight is a fungal disease that largely affects Buxus sempervirens (Box) and its cultivars.
Two fungi are the common cause- Cylindrocladium buxicola (syn. Calonectria pseudonaviculata) and Pseudonectria buxi. Identification is best in wet conditions. White spore masses on the underside of infected leaves signifies C. buxicola, whereas P. buxi spores are pink. Both can exist on the plant at the same time but C. buxicola will be the one causing the most damage.
What should I look out for?
Autumn and Winter is usually the time when you may see the first signs of box blight.
The common symptom is dark brown or black spots appearing on the Box leaves. These will merge to cover the entire upper leaf surface and soon after the leaves will fall off, leaving twiggy, bare patches on the Box.
Look closer and you may see black streaks on the stems. This is caused by the C. buxicola fungus and will cause die-back on the Box plants.
What can I do?
Box blight is not a death sentence for your plants.
If possible, cut out any severely affected areas. As far as is practicable clear any fallen leaf litter and dead material. Destroy both, ideally by burning. Do not put any Box leaf litter, cuttings or dead material in your compost as the fungus spores can remain viable for at least 6 years. Fungus can also remain in soil so best to remove and replace the topsoil around the affected plants.
Make sure the Box plant is as strong and healthy as possible to improve recovery and increase infection resistance. Do this by mulching annually in Spring with a good depth of quality mushroom compost or leaf mould to help improve the nutrient balance in the soil. Spray the Box plants with a liquid seaweed or Topbuxus every six weeks during the growing season to promote healthy growth.
Increase air movement through the Box plants by reducing the amount of times the box are trimmed. Regular clipping encourages denser growth, which is an ideal environment for the fungus to flourish. If your box is in a border or flower bed, best to reduce overcrowding and improve air movement by removing any other plants growing in close proximity.
Avoid overhead watering as spores can be spread in the water droplets and damp leaves create conditions that the box blight fungus thrives in.
Keep shears, clippers and hedge trimmers clean when trimming infected box to avoid spreading the box blight to healthy plants. Do this by dipping tools in a weak mix of bleach every so often when working, or apply to the blades using a trigger sprayer. One small capful of bleach to five litres of water works well.
Treat the Box plants in Spring and Autumn with a commercial grade fungicide. Applications must be delivered by fully qualified operatives who are certificated by NPTC (National Proficiency Tests Council).
Following this advice does not guarantee success at curing box blight but will certainly improve the chances of the Buxus (box) battling the fungal disease. Remember to continue with the fungicide treatments and good gardening practices even when your Box plants start to recover, to ensure the box blight does not return.
Take a look at the two photos from a garden where I currently work. The first photo was taken in early Spring and shows box hedging badly affected by box blight. The second photo was taken a year later in early Summer, after treatment with fungicides. The Box plants have recovered really well and although there are still a few signs of box blight, the hedge is looking stronger, healthier and with lots of encouraging new growth.
Please contact me if you are concerned about box blight in your garden or would like to know more about my fungicide treatments to combat the disease.