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Box tree caterpillars feed within webbing and can completely defoliate box plants. It is a relatively new insect to Britain. Whilst the adult moth was first reported in Britain in 2007, caterpillars were not found in private gardens until 2011, it has since become widely distributed across England (particularly London and surrounding areas) and is present in Wales, Scotland, Northern Ireland and Ireland.
Box tree caterpillar
Box tree caterpillars are the larvae of a moth that feeds on box (Buxus) plants. It is native to East Asia and it became established in Europe in 2007. Although the first adult moth arrived in Britain during 2007, followed by several moths to light traps in 2008, it was not until 2011 that larvae were reported in private gardens in the home counties. By the end of 2014 the moth had become established in parts of London and surrounding areas; in many cases the caterpillars causes severe defoliation. For growers in the south-east of England it is now a problem that is likely to reoccur repeatedly throughout the growing season and in successive years. The moth is also becoming more widely established in England, parts of Wales and Ireland.
Seen box tree moth? We would like to know.
As part of our research the RHS would like to know where box tree moth has been seen.
Please submit your records via our box tree moth survey (expected time to complete survey = two minutes).
Submissions to our pest and disease surveys are stored permanently in an anonymised form in order to monitor the spread of the pest or disease. We may contact you within 2 months of your submission in order to verify your sighting but your personal data will not be permanently stored in connection with your submission and will be deleted after 1 year. We publish and share only non-identifiable data from survey submissions (such as a six figure grid reference) with third parties and the public for the purposes of scientific research and advancing understanding among gardeners.
Between 2015 and 2016 over 800 records of the moth were received, this jumped to over 3000 in 2017, and over 6 000 in 2018. The records show that the moth is a widespread problem in London and surrounds and is becoming established throughout much of England and parts of Wales. It was also reported for the first time in Ireland in 2018.
Thank you to everyone who has submitted records so far – read a blog about the surveys
Watch an animated map of the results from the box tree caterpillar survey (links to YouTube)
Gardeners are likely to become aware of box tree caterpillar when they find webbing and caterpillars on box plants.
Pesticides for gardeners (Adobe Acrobat pdf document outlining pesticides available to gardeners)
Biological control suppliers (Adobe Acrobat pdf document)
Where it has become impractical to control box tree caterpillar an alternative hedge or topiary plant can be used. Ongoing trials of a variety of compact, evergreen shrubs at RHS Garden, Wisley are showing promise as alternatives. The following all have small leaves and can be clipped into formal hedging styles:
Berberis darwinii 'Compacta' Berberis thunbergii ‘Atropurpurea Nana' AGM Elaeagnus × submacrophylla 'Compacta' Euonymus fortunei (various cultivars) Ilex crenata Lonicera nitida 'Maigrün' L. nitida 'Baggesen's Gold' AGM Luma apiculata 'Glanleam Gold' Osmanthus delavayi AGM Pittosporum 'Arundel Green' AGM P. 'Collaig Silver' P. 'Oliver Twist' P. tenuifolium 'Golf Ball' (PBR) Podocarpus 'Chocolate Box' P. 'Young Rusty' Rhododendron Bloombux ('Microhirs3'PBR) Taxus baccata 'Repandens' AGM Ugni molinae, Ugni molinae 'Butterball'
The biology of the box tree caterpillar in Britain is not yet fully known, as it is a recent discovery here, but it may have two or three generations per year. It overwinters as small caterpillars, hidden between box leaves that have been spun together with silk in late autumn, and completes its development in spring. The adult moth is capable of flight, but it is not known how far it can travel.
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