DEAR SIR:

In response to the feature on ‘Japanese knotweed hitting agriculture’ (Irish Farmers Journal, 5 August), the plant is spreading rapidly, damaging buildings and costing thousands to eradicate.

Japanese knotweed was first found in Wales in the 1880s. It was introduced by the Victorians for horticulture. Its 3 metre t0 4 metre (10ft to 13ft) stems, ornamental leaves and clusters of white flowers made it an attractive option for gardens.

But now, the weed, one of the most destructive plants, not only causes great damage to plant biodiversity and agriculture, it is also causing problems for buildings and flood defences.

Kerry County Council has put aside €100,000 in a bid to destroy the invasive weed, which has stymied construction of a community hospital in Kenmare and covers the banks of the River Laune near Killorglin. Several clumps of the invasive non-native herbaceous perennial were discovered alongside the N22 near Killarney.

Japanese knotweed must be destroyed by repeated sprayings rather than cutting, since loose fragments cause it to spread. Once a leaf or trimming takes root, that’s the end of the garden.

Scientists at the UK Centre for Agriculture and Biosciences International have been licensed to test insects – a psyllid or plant louse called Aphalara itadori – since 2010. The controlled release of insects which feed on the weed is being evaluated in Wales.

The insects, imported from Japan, will stunt the super weed, allowing native species to flourish. UK, landowners who fail to control the weed could be fined or receive anti-social behaviour orders.

Read more

Japanese knotweed could affect farm payments

The plight of noxious weeds on Irish farms

Letter: dealing with Japanese knotweed

Identifying the dreaded invader: Japanese knotweed