The Powerscourt Estate has proactively been substituting almost 80% of its boxwood shrubs to ward off a possible attack by box tree moths, as Alex Slazenger, the chief gardener explained. The menacing box tree moth and its destructive larval form are yet to be detected at the estate, but gardeners anticipate an outbreak owing to global warming trends.
The damaging insect is native to East Asia but surfaced in mainland Europe in 2007, before being reported in Ireland in 2017. Supposedly, boxwood plants carrying the infestation were unknowingly transported. The moth thrives in UK weather, hence, is expected to adapt easily to Irish weather conditions too. The pioneering record of a specimen in Ireland was trapped in Waterford and it has subsequently been identified in numerous regions including Dublin, Cork, Waterford, Wicklow, Laois, Kildare, Clare, Donegal, Antrim and Down.
The moth’s larvae are particularly harmful as they consume both the leaves and bark of the box tree, leading to plant death. In Ireland, they do not have natural predators to keep their population under control.
In response to this threat, Powerscourt Estate has replaced 500m of box tree shrubs with a lower risk alternative, the dwarf Japanese yew hedging. They have also discouraged the planting of box trees.
The decision to proactively restructure the landscape, despite the absence of the moth was taken to support sustainability, as the chemical used to exterminate the moth is highly toxic. “We’ve observed widespread infection around Dublin. However, we intend to avoid chemical use if we do encounter them,” commented Slazenger.
Meanwhile, a resistant strain of fungal disease, box blight, has infested and killed some of the existing box trees on the estate. Slazenger mentioned that a rise in fungal diseases and pests has been noticed due to climate change. “Our traditional reliance on chilly winters to combat the blight has been ineffective,” he noted.
To keep the box tree moths away, Powerscourt Estate is implementing various preventive strategies. Slazenger emphasized that the moths have the capability to “devastate flora overnight”.
Certified by Sustainable Travel Ireland, Powerscourt is Ireland’s premier pioneer in sustainable travel visits. The chief focus is sustainability, as pointed out by Mr Slazenger. He emphasised the ongoing changes in the garden, tailored towards a sustainable future and reduced chemical usage.
The gardeners are engaged in a strategic development termed ‘climate matching’ to allow the gardens to adapt to the climate, as part of the garden’s future-proofing plan. “Our selection of plant species is based on their survival potential,” explained Mr Slazenger. “The emergence of new pests and diseases is not a novel occurrence. Their spread across the globe is largely due to climate change,” he added.
In the past few years, box hedges, particularly at public sites such as St Stephen’s Green, managed by the Office of Public Work, have suffered from Box or Buxus blight. This has prompted a shift towards alternative hedge options, with yew and euonymus taking precedence.