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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 the UK in 2008, caterpillars were not found in private gardens until 2011, it has since become widespread in London and surrounding areas.
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 adult moths were first found in the UK in 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 counties; in many cases the caterpillars had caused severe defoliation indicating that the moth is likely to become a serious problem.
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). The RHS confirms that your information will be stored in compliance with the Data Protection Act and personal data will not be shared with third parties. If you prefer not to have your information used in this way, please indicate when submitting your record.
Between 2015 and 2016 over 800 records of the moth were received, this jumped to over 3000 in 2017, indicating that the moth is a widespread problem in London and surrounding areas.
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.
Choose alternatives to box
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 crenataLonicera nitida 'Maigrün'L. nitida 'Baggesen's Gold' AGMLuma 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' AGMUgni molinae,U. molinae 'Butterball'
Pesticides for gardeners (Adobe Acrobat pdf document outlining pesticides available to gardeners)
Biological control suppliers (Adobe Acrobat pdf document)
The biology of the box tree caterpillar in the UK 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 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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