Box blight is a devastating fungal disease that attacks the leaves and stems of box (Buxus) plants. The affected leaves quickly turn brown, often with a yellow discolouration, and fall off the plant. Even quite moderate attacks can lead to extensive defoliation and creates large bare patches.
The disease may also attack stems, particularly young ones, producing black marks and causing them to die back.
Closely trimmed plants, such as topiary, are generally more prone to infection than unclipped ones.
Box blight spreads very quickly in warm, humid conditions.