Box tree caterpillars: why we might have to get used to the ‘worst pest in Britain’

Name: Box tree caterpillar.

Age: About four weeks as a caterpillar, then a few weeks more as a moth.

Appearance: Beautiful long green-and-black stripes dotted with black circles and yellow hairs.

Habitat: Your hedge.

Diet: Your hedge.

Argh! I’m afraid so. In fact, these pests can quickly defoliate an entire box hedge, and are now doing so all over the south of England.

Is a box hedge a hedge in the shape of a box? Often, although box (or buxus) is really the name of the type of shrub that is frequently clipped into formal squares, topiary animals, mazes and so on.

Yes, my garden in the south of England has several of those. So, how come they’re only being chomped by these caterpillars now? Well, the box tree caterpillar is an invasive species. It only arrived in Europe from east Asia in the last 10 years, and the first caterpillars were reported in Britain in 2011.

It’s a Chinese invasion! Probably. Last year, the Royal Horticultural Society, which is like the AA for plants, received more inquiries about these caterpillars than any other pest; there were 122 inquiries about slugs and snails, which came second, compared with 433 about the box tree caterpillars.

Won’t that just reflect the fact that gardeners already know about slugs and snails and don’t need advice, whereas these caterpillars are new to them? Shush. The point is that the box tree caterpillar is a major problem, and it’s on the march.

But how can we stop them? Er … Don’t know. There are things to try, but they all have drawbacks. In east Asia, their population is regulated by predators that we don’t have here.

Let’s import some, then! I wouldn’t recommend it. The main one is the Asian predatory wasp, which has a very nasty sting and is itself an invasive species in south-west France, where it is a threat to bees.

Curse these marauding foreign hordes! Yeah, maybe. Sometimes it’s a matter of getting used to things. Remember that, in Britain, we are an invasive species. It was all Neanderthals round here until Homo sapiens came along and eventuallly drove them to extinction.

At least we didn’t eat their hedges. No. There is that.

Do say: “They come over here … devouring our topiary …”

Don’t say: “We must take back control of our herbaceous borders.”