Experts Report Rising Numbers of Box Tree Moths

Experts anticipate that a moth species, whose caterpillars are capable of destroying the foliage of box plants, will likely become more prevalent in north-east England. The box tree moth, originally an Asian species, arrived in England in 2007 and has since established itself in south-east England. The species was first recorded in the North East in 2017, and Dr Dave Wainwright, from the Butterfly Conservation charity, indicated that its numbers are increasing. Dr Wainwright noted that the moths have crossed the River Tees within the last couple of years and are “pushing northwards.” The box caterpillar is identifiable by its yellow and black stripes along its body and a black head. This moth has been problematic for gardeners in the South East, leading the Royal Horticultural Society (RHS) to issue a warning earlier this year. Dr Stephanie Bird, a plant health scientist at the RHS, stated that the majority of the insect’s population is concentrated in London and its surrounding regions, but it is expanding its range and is expected to become “more common in more northerly places” where box plants are cultivated. According to data from Butterfly Conservation, there were 37 sightings of the moth in County Durham and north of the Tees from January to September this year alone, an increase from 27 for the entirety of 2023. Dr Wainwright, who serves as head of conservation for England at the charity, explained that some of these records would have represented multiple moths observed on the same night. He commented, “They’ve certainly increased in the last year or two.” Over the years, sightings have also been documented in Newbiggin and Amble in Northumberland, Tynemouth in North Tyneside, and Gosforth in Newcastle. In August, an adult box tree moth was discovered for the first time at Washington Wetland Centre, located near Sunderland. Dr Wainwright described this as “significant” for the region and predicted it was “only a matter of time” before the moths spread further north. He remarked, “I think if we were to have this conversation in 10 years, everyone would be absolutely sick of the sight of them because the caterpillars would be feeding on the box trees in the gardens.” Dr Bird stated she was not surprised by the sighting, although the species remains less common further north. She attributed the spread partly to the plant trade and noted that the moths are also “quite strong flyers.” By the end of September, the RHS had received more than 6,457 reports of box tree moths nationwide. The responsibility for managing the potential problems caused by the caterpillars currently falls to gardeners and councils. The RHS is also researching natural predators of the moth, which include certain parasitic wasps and spiders. Darren Evans, professor of ecology and conservation at Newcastle University, described the caterpillars as a “real problem” for gardeners, capable of completely stripping plants when present in large numbers. He advises against using pesticides and suggests removing the caterpillars by hand instead. Professor Evans stated, “We should expect to see not just this type of moth, but a whole range of other species here in the North East driven by climate change.” He added, “We have either got to think carefully what alternative plants we can grow in our gardens, or just recognise that they are now an established part of our biodiversity and just leave them be.”