The very hungry caterpillar: say goodbye to London's number one garden pest in these easy steps
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Box is the backbone of London gardens, whether as hedges or clipped into domes and spirals. But Buxus is under serious threat.
Over the summer the box tree caterpillar has been quietly trashing our city gardens. This very hungry caterpillar can strip mature bushes of leaves in just a couple of days.
Recently the cook and writer Nigel Slater announced on Twitter that he was removing the caterpillar-infested box plants from his Islington garden.
“Today, with a somewhat heavy heart, I made the decision to rip out all the box hedges and topiary,” he tweeted.
“It survived the dreaded box blight but has finally succumbed to the box tree caterpillar. The lot reduced to a grey skeleton in one week.”
Actress and broadcaster Anneka Rice, who also lives in London, has replaced the box plants in her garden with olives and lavender.
For the first time in 10 years, slugs and snails have been toppled from the Royal Horticultural Society’s number one garden pest spot, their place taken by the Asian box tree caterpillar which arrived in west London in 2011, probably imported on plants from Europe.
The RHS cites a 66 per cent rise in reports of the pest over this time last year. Most London garden designers now avoid planting box.
It’s not the first time box has taken a beating. Box blight has also been a problem for several years, a fungal disease that can kill the plant.
Small patches can be treated with pruning, fungicides and the foliage spray TopBuxus Health Mix (topbuxus.com).
It’s no wonder battle-weary Londoners are pulling out their hair over these box foes.
However, Richard Barley, director of horticulture at Royal Botanic Gardens Kew, which has seen infestations of the caterpillar for the first time this year, says we shouldn’t give up.
“The impact of caterpillar is far quicker and more obvious than blight damage but though it seems more dramatic it’s just taking the foliage off, it’s not killing the plant,” he says.
“Box caterpillar can be controlled. It’s just a question of timing and the right application.”
Box grows slowly, so replacing mature topiary can be eye-wateringly expensive.
“There are many years invested in making a good topiary and you want to try to save it,” agrees Barley. “There are chemical treatments but some are only available to professionals, which narrows the window for home gardeners. It might be worth getting a contract company.”
One product said to be very effective against caterpillars, XenTari, is not yet licensed for home use in the UK. Some desperate gardeners have apparently got round this by buying it on Amazon from Europe.
Otherwise, call in professionals licensed to use similar chemicals, or persevere with off-the-shelf insecticides such as Bug Clear Ultra which may or may not be up to the task.
The RHS website’s box tree caterpillar page has a list of approved products.
What can you use to replace box?
London designer Charlotte Rowe (charlotterowe.com) finds Japanese mock orange (pittosporum tobira Nanum) and Japanese holly (ilex crenata) are good in pots.
“If we are doing domes/balls in gardens we might use a combination of ilex crenata and taxus baccata [yew],” she says.
Fellow designer Matt Keightley (rosebanklandscaping.co.uk) agrees and also finds euonymus japonicus Green Rocket good for low hedging. Kew’s Barley suggests rosemary, Chilean myrtle and berberis.
But don’t just take their word for it. To see how these evergreens could look in your garden, head to RHS Wisley (rhs.org.uk/gardens/wisley) where curator Matthew Pottage has been experimenting with alternatives to box in the Walled Garden.
He’s particularly excited about the potential for podocarpus nivalis, a New Zealand plant that can survive cold winters, and he’s also trying out a small-leaf rhododendron Bloombux and holly-leaved berberis darwinii Compacta.
A cultivar of yew called Repandens makes good low hedging, he says. But ilex crenata? “We splashed out four years ago on big, cloud-pruned pieces which took two years to die slowly. They’ll end up on the bonfire.”
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