Fine Gale senator Tim Lombard said the badly needed 56-house project at Beechgrove in Clonakilty is on hold due to the presence of the plant at the site.
“The resulting financial consequence is high,” he said. “The estimated cost of construction for the Clonakilty housing project is €8.7m which will only increase due to these eradication delays.
“To save the future cost, which will only increase incrementally the longer the problem is left, action must be taken now.”
Cork County Council officials confirmed they have been receiving reports of knotweed infestation on a near daily basis and are finding it increasingly difficult to destroy the weed with their own resources.
Very few towns and villages in Cork are reportedly free of the plant which, if cut, multiplies rapidly.
Treatment processes can take as long as four years to destroy the knotweed which can destroy buildings.
A special working group has been established by the council to tackle the issue.
However, it has been estimated that invasive species, including knotweed, cost the Irish economy around €260m yearly.
Mr Lombard said local authorities have struggled to deal with the issue. He blames the current strategy where the efforts of state agencies working on an individual basis are not extensive enough to eradicate such invasive plants.
“Invasive plants, especially Japanese knotweed, have become very prevalent in Ireland over the last few years,” he said. “It is presently a substantial financial and labour-intensive burden that will continue to endure and will only accrue a much larger future obligation if not dealt with now.
“To give an international example of the cost involved, £70m was required to clear Japanese knotweed from the Olympic village site in London in 2014. Appreciating the magnitude of the issue, the UK has allocated a national budget of £5bn per year towards addressing this problem.”
In Britain, knotweed on private land seriously damages prospects of a sale.
Mr Lombard said the responsibility of dealing with invasive plants comes under the Department of Regional Development, Rural Affairs, Arts and the Gaeltacht. Instead, he said the issue needs to be dealt with directly by the Department of Environment which would have the ability to co-ordinate the local authorities, the NRA, the Inland Fisheries, and Iarnród Éireann in a national taskforce.
A tidy towns’ group in Glounthaune, in East Cork, has spent significant money and man hours trying to eradicate more than 80 knotweed plants in its area. It purchased special injection guns in Britain and injected an estimated 120,000 stems with a special weedkiller in an effort to kill off the plants.