Green alert Posted on August 16, 2015

I reported from the Hanbury Garden at La Mortola in February last year that I had seen a nasty new threat to box plants. Little did I think that only a year later it would have arrived – right here, in our garden and our neighbours’.

It’s called Cydalima perspectalis. In Italy they call it Piralide del Bosso. So far it’s only Box Caterpillar here. The caterpillars are green, yellow and black, up to 4 cm long, and the moth brown and white. But it’s the larvae, from yellow eggs laid on the underside of the leaf, that do most of the damage. They protect themselves with something like a fine miniature spider’s web while they’re at it. They eat whole box leaves or leave the skeleton; in any case defoliating the plant and ruining its appearance for – how long? In some cases there are signs of new leaves growing out, but one must presume that the damage is debilitating and could end in dead box.

At first it’s not easy to spot. There are often little brown patches after trimming a hedge. But look closely: the little webs are not hard to see. It spreads quickly; there’s no time to waste when you see it. Look at the RHS website; it’s not particularly encouraging.

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