The gardeners’ salvation? Jackdaw develops taste for the vicious Box Moth caterpillar

Jackdaws have been seen feasting on box tree moth caterpillars, who have wreaked havoc in domestic, commercial and historical gardens.

Gardeners at Ham House, Richmond, may have finally found a solution to the pesky box tree moth caterpillar.

The insects have been wreaking havoc on the historic garden and until now, horticulturalists had been struggling to find a way to kerb them.

Box hedges at the Ham have been stripped of their leaves and risk being killed completely by the greenish yellow larvae.

The public garden is not alone in its plight, with green spaces throughout Britain being affected, particularly those in the southeast.

The gardening team had employed thyme oil and even caterpillar waste to try to stop the pest in its tracks, but efforts have proved unfruitful.

However, in recent months gardeners have spotted jackdaws eating the caterpillars, and it appears they have developed a taste for the bugs.

Jackdaw hunts for caterpillar

A jackdaw hunts for box tree moth caterpillars. Credit: Sally Robinson (National Trust).

‘We first noticed jackdaws plucking caterpillars from the box hedges in May, which was fantastic to see, but I thought it might be a one-off,’ said Rosie Fyles, head gardener at Ham House.

‘Box hedging is an iconic part of the garden at Ham, and with so much of it, the threat of damage from the caterpillar was huge.

‘So we were thrilled when the birds returned in August for the next lifecycle. We had wondered if the caterpillars would be unpleasant or even poisonous to native birds — but the jackdaws have clearly developed a taste for them.

‘It’s early days, but it’s a really encouraging sign that there may be a homegrown solution yet.’

The box tree moth (Cydalima perspectalis) is native to Asia and was first reported in the UK in 2008.

In China, the insect is controlled by a parasitic wasp, but until now it had no known predator in the UK.

Ham House

Sunrise over Ham House’s stunning gardens. Credit: Sally Robinson (National Trust).

Ham House’s kitchen garden was badly damaged during the first life cycle of the caterpillars in the spring, but with the help of around 10 jackdaws regularly patrolling the hedges, the box has partially rejuvenated.

Gardeners at the 17th-century estate are now exploring ways to attract more jackdaws, and other birds, including changing the way they prune the hedges.

‘We’ve noticed the jackdaws are most effective on the hedges which have been partially stripped of leaves by the caterpillars and so contain bigger holes — which makes the insects easier to spot,’ added Rosie.

‘We’re now looking at ways to prune the hedges in a more open style, that allows increased air flow and gives the birds easier access to the caterpillars.

‘Nature is the heart of everything we do at Ham, and sometimes that means we have to be pragmatic where we want to be perfectionist.’


How to get rid of box moth caterpillars

The box moth, Cydalima perspectalis, and its caterpillars quickly destroy box plants. Here's how to combat these pests.