The images below are of the Box Tree Moth (Cydalima perspectalis) in both the caterpillar and mature stages. This little darling can produce two to three generations during the growing season, with the caterpillars rapidly defoliating Box (Buxus) plants. As shown in the photograph, the caterpillars will also produce a webbing which covers the leaves of the plants whilst they pupate.
They are most active between April through to October, and are especially prevalent in the south-east of England. Check box plants frequently from early spring onwards so action can be taken before a damaging population has developed.
To try and prevent damage, it is best to pre-empt the eggs being laid. Pheromone traps are available from a wide range of sources. The traps will attract the male moth, helping you to monitor activity and pre-empt the emergence of the caterpillars (moth mating and egg laying will not be eradicated, but should be reduced). The next stage is to treat the caterpillars by applying a nematode spray (the most succesful nematode in treating Box Tree Moth is Steinernema carpocapsae). These shoould be applied as soon as caterpillars appear.
A quick internet search will help you find out more, and find suppliers of the nematodes and traps, but for ease of effort, and more information check https://dragonfli.co.uk/ and https://www.koppert.co.uk/challenges/pest-control/caterpillars/box-tree-moth/ as well as the RHS website.
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