ANNE SWITHINBANK’S MASTERCLASS
What to do about box blight and alternate hedges
QBox blight and box caterpillar have destroyed our low hedging. Is there anything that will treat it? And what would be a good alternative to box? Wendy Brownleigh, Basildon, Essex
A
For thousands of years, the ability of box to withstand clipping has suited a human desire to shape and control. The ancient Egyptians are believed to have used it; the Romans did and no knot garden or parterre could be without it.
Today, box hedges, spirals and balls are found in domestic gardens but the plant is now under threat from box blight, Cylindrocladium buxicola, which first appeared in the mid 1990s, and box moth caterpillar, a problem from 2008.
With box blight you’ll notice black spots on foliage, leaves dropping, black streaks on stems and, in wet conditions, white spores. Like most fungal diseases, by the time symptoms appear it already has a hold and is hard to control. Secondary infection from Volutella buxi causes leaf browning and wilting but leaves tend to hang on, and sprout pink spores.
To try and save plants, clear-up and dispose of all infected leaves (blight spores remain viable on these for six years) and cut out infected material, while pruning to improve air flow. Avoid feeding, which encourages vulnerable soft growth, but mulch instead. Some fungicides help but you would have to begin spraying when new growth starts in spring and repeat often.
To beat box moth caterpillar, inspect box regularly from April to September as there are two to three generations before the last batch of caterpillars cocoon for winter. Look for webbing and bright yellow-green caterpillars with black spots and white dots. Pheromone traps lure adult males. The moths are white with a brown border and wingspans of 1.5in (4cm). Remove caterpillars by hand or use nematode biological control. Insecticides are available but you don’t want to harm pollinating insects.