Box blight

What you see

Dark brown or black streaks up the stems, leaves turning bronze then straw-coloured and dropping in patches, leaving bare pockets in the hedge. In humid weather a fine white bloom of spores appears on leaf undersides.

Conditions

Warm and very humid with prolonged leaf wetness. Spores are sticky and travel on tools, gloves, clothing and clippings rather than far on the wind.

Treatment

Cut out affected sections well beyond the damage, bag the clippings on the spot, and disinfect tools before touching any other box. Reduce watering and open up the planting.

Prevention

Clip in dry weather only. Never clip a wet hedge. Disinfect shears between plants. Avoid overhead irrigation. Consider replanting with Ilex crenata, which looks similar and is immune.

Months: May, June, July, August, September, October

Plants

Box

Remedies

Bordeaux mixture (copper)

The thing people get wrong

The spores are sticky rather than airborne, which changes everything about how it spreads - it moves on the gardener, not the wind. A single pass with infected shears down a long hedge does more damage than a year of weather. Clip dry, disinfect between plants, and never bring box clippings from elsewhere onto the property.