The box tree moth only arrived in the UK from the Far East in 2008 but experts warned that it is spreading rapidly.?Its hairy caterpillars devour the leaves of the plant widely used in hedging and topiary and also kills it by attacking its bark. Box tree moths?protect themselves by covering the plant in a white cocoon, and in good conditions the moth can have three generations in a year.
In 2015 and 2016 the Royal Horticultural Society received more than 800 records of the moth showing that it is now a widespread problem in London and surrounding areas.?RHS principal entomologist, Andrew Salisbury, said: “It appeared in France in 2005 and spread across Europe before getting into the UK.?Now the population is surging in Buckinghamshire, Essex and London.”
The caterpillars can ruin garden displays but also pose a threat to native wildlife because box is popular with bees and provides a dense, sheltered habitat for small birds, mammals and insects, according to the Woodland Trust.?Typical signs of an infestation include feeding damage on the leaf edges, with sometimes only leaf skeletons remaining.?The moth’s natural home is the Far East, across China, Korea and Japan.
The Invasive Species Compendium of the Oxfordshire-based Centre for Agriculture and Bioscience International says it is thought to have brought in accidentally on box plants imported from the Far East. CABI says it has already devastated large areas of trees on the continent and can spread at a rate of about six miles a year.?It can survive in regions from temperate to tropical and could spread to the whole of the UK apart from northern Scotland.
The moth has a wingspan of under 2in and is usually white with a dark brown border.?The caterpillars are light green with black stripes with white dots.?RHS Chief Horticulturalist Guy Barter said the caterpillar turned up in the society’s HQ garden at Wisley in Surrey last year.?He said: “The initial reports were from the Epping area but it has now spread all through London.?It seems to be prevalent now across neighbouring European countries. If it can withstand their winters it can withstand ours.
“We had an infestation at our garden at Wisley last year. We managed to wipe it out by spraying it with an insecticide.?But we need more monitoring and control of the movement of plants around the world, particular those grown in soil. Other diseases brought into Britain include ash dieback and, in Devon, an outbreak of chestnut blight.?Amateur gardeners can help by not bringing plants back from their foreign holidays. Packeted seeds are the safest option.”