What are box tree caterpillars?
Box moth (Cydalima perspectalis) is an invasive moth species first seen in Britain in 2008. Its destructive larvae were discovered in gardens in 2011. Box moths originated in the Far East and are now established in London and the Home Counties with reported sightings in 2017 as far north as Cheshire and Humberside.
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How to spot box tree caterpillars
Box tree caterpillar eggs are laid on the underside of box leaves and are yellow and flattish.
Young caterpillars are just over an inch long and a greeny yellow colour with black and white striping.
The older caterpillars protect themselves from predators by building a distinctive pale white tent of webbing when they feed.
The adult moth has white wings edged with brown and is just over an inch wide from wing tip to wing tip.
In winter the small caterpillars hibernate in an envelope of two box leaves that have been spun together the previous autumn.
Adult box tree moth
What plants are at risk?
Box tree caterpillars will completely decimate box (Buxus).
What damage can they cause?
The caterpillars eat the foliage and in really bad cases this can defoliate the plant causing dieback.
How to get rid of box tree caterpillars
1. Pick them off by hand.
2. Try using a pheromone funnel trap. These cost around £25 from Agralan and can be set from mid March to October.
3. Chemical sprays are best used on the young caterpillar as you need a lot of spraying to penetrate the webbing. Avoid using chemicals when the box is in flower or near flowering plants as it can harm pollinators.
Have you seen box tree caterpillars or moths?
If so please report your findings to the RHS by following this link.
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