Friday 1 April 2016
An invasive caterpillar which feeds on the leaves of box trees has been named 'top pest' by the Royal Horticultural Society and is a threat to the rare wild box trees of the Chilterns, including the largest native box woodland in the country.
The box tree caterpillar originates from Asia and was discovered in England in 2011, possibly arriving via imported goods. It's now spreading across south east England and in 2015 it accounted for the biggest number of enquiries about pests received by the RHS.
The caterpillars feed on box leaves and are capable of defoliating an entire plant. Box is commonly known as an ornamental tree and a low hedging plant in formal gardens. It does also exist in the wild in England, growing on chalky soils, but is far less widespread than previously. There are only three formally-recognised native box woodlands remaining in the UK, and the largest of these is on the edge of the Chiltern Hills near Great Kimble in Buckinghamshire. Smaller stands of box, including some veteran trees, are dotted throughout the Chilterns.
It is not known for certain if any Chilterns box has been attacked yet by the caterpillar but the Chilterns Conservation Board is asking the public to be vigilant and keep an eye out for the pest on domestic plants and wild ones. The RHS are also asking people to report any sightings of the caterpillar.
If spotted the caterpillar can be controlled by physically removing it from the plant or by using a biological control or insecticide. It is also advised to carefully check box plants before buying to make sure they are not infected.
The Board's Box Woodland Project has helped secure a future for native box by collecting and storing native seeds at the Millennium Seedbank, creating a stock of native box seedlings and producing free guidance about managing native box.
More information on the box tree caterpillar Cydalima perspectalis