I popped in to see my friend Jane the other day and we sat on her terrace overlooking her beautiful garden. She spends hours making sure it is gorgeous, full of healthy-looking shrubs and flowering plants, but she said she had suffered somewhat of a tragedy over recent days. A shrub that she had planted more than 10 years ago seemed to die overnight.

She couldn’t recall its name but said: “It was beautiful with variegated green and yellow leaves, and one day it was fine, and the next it was completely dead!”

Jane had noticed in the days running up to its mysterious demise that it was covered in what looked like cobwebs, and then when it had died and she looked closer, she realised it was infested with caterpillars.

With the help of her husband, they dug up the sad tree, chopped it up and disposed of it in her green waste bin, at the same time as picking off and exterminating as many caterpillars as they could find. They both love animals and nature and weren’t happy at permanently getting rid of the creatures but reasoned that if they can destroy a whole shrub overnight, they cannot be a good thing to have in your garden. Sentimentality went out of the window.

I asked what the caterpillars looked like, and wondered which butterfly or moth they would eventually turn into. Jane showed me her bin with the remains of the brown and withered shrub and there were dozens of the critters still crawling around it. The caterpillars were a couple of inches long with green and black stripes and a black head, and clearly, they hadn’t managed to capture all of them.

Well, this is the kind of murder mystery that the Countryman’s Daughter thrives upon, and as soon as I got back home, I donned my detective hat and set to work. It took me a good minute of eager Googling to crack the case wide open.

Jane’s plant had been slaughtered by the Box Tree Strangler - I mean Caterpillar.

The Box Tree Caterpillar, which is active during spring and summer, is an invasive species that the RHS says is becoming one of the most common problems in British gardens. It predicts that 2024 will be a bumper year, with five times as many cases reported in the first four months of this year than last. This very hungry caterpillar stowed away on plants imported from east Asia in 2007, although the first moth found in a private garden was not reported until 2011. It quickly became a significant problem in the south east, and steadily began to make its way north, unfortunately landing in Jane’s garden this week.

The box tree is a common sight across the land, often being clipped into geometric shapes or animals by those fond of topiary. If you’ve been to places like Castle Howard, Broughton Hall or Beningbrough Hall, then you’ll have seen some fine examples. But if you have some in your own garden, you need to start regularly inspecting it for this particular critter. If you shake your box tree and moths fly out, then that’s a sure indicator they are laying eggs, so you need to get on the case pronto. The moth (Cydalima perspectalis) has white wings with brown borders, or sometimes is brown all over, and lays its eggs on the underside of box leaves. The eggs are flat and yellow and overlay each other, a bit like tiny fish scales. Initially, the problem can look like box blight, a fungal disease, but a tell-tale sign is the web-like substance that can appear all over the tree. The caterpillars weave this over their feeding area, and once you see that, they can decimate a whole tree within days.

Thankfully, they are only interested in the box tree, so a sure way of keeping them away is to not keep any in your garden. Even when a tree or hedge looks dead, though, it can be rescued with effort and persistence and there is lots of advice online. If you discover it, then you should report it (again online is the place to go to find out how).

One last question - if box tree caterpillars destroyed all the box in the land, would they die out?

Do you have opinions, memories or ideas to share with me? Contact me via my webpage at countrymansdaughter.com, or email gazette@gazetteherald.co.uk.