WHAT DOES BOX CATERPILLAR LOOK LIKE?

What does a Box caterpillar look like?

You don't need to keep you eye off the ball for long for your prized box plant to become decimated by Box caterpillar - Cydalima perspectalis . They are usually well hidden, well camouflaged and when you do notice some unusual damage on your box plants the accompanying webbing can be ignored as belonging to over-active spiders. However, move aside the foliage and once peering inside you can be surprised, or perhaps I should say shocked, at just how many Box caterpillar can be found hidden among the shadows. So just what does a Box caterpillar look like?

Box caterpillar moth
Well if you are on your toes you may spot the eggs. These are pale yellow and flattish, and are laid sheet-like, overlapping each other on the underside of box leaves. Newly hatched, young caterpillars are are greenish-yellow, with black heads but this changes as they mature. Typically, you are likely to  spot Box caterpillars when they are at their most active which will be when they are 25–30 mm long, green coloured with browning longitudinal lines.

The caterpillars eat the box leaves, in particular any new growth, and produce webbing over their feeding area, often hiding in a leafy tube held together with yet more webbing. Plants may also show patches of die-back which may be especially apparent on trimmed plants. Heavy infestations can create serious die back that does not grow back in subsequent seasons.

However, to try and avoid any damage to your Box plants it is advisable to try and  spot the moths themselves before the eggs are laid. These can be attracted using pheromone traps, and while these are not particularly good as a control method they are great as a tool for overall management.

Native to Japan, China, Taiwan, Korea, far-east Russia and India, there are two variants of the adult Box caterpillar moth observed. The first and by far the most common found in the UK has conspicuous white wings with a faintly iridescent brown border. the second variant is almost entirely light brown. Both colour forms have a wingspan of around 4 cm.

Main image credit - böhringer friedrich - Own work, CC BY-SA 2.5, https://commons.wikimedia.org/w/index.php?curid=20484379

In text image - By Didier Descouens - Own work, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=33203392

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