Invasive plant in over 60 locations in county cavan

Damian McCarney

As hedge-cutting season continues, farmers are being warned to avoid cutting an invasive plant species, which has cropped up in over 60 locations county-wide and can destroy buildings. In a bid to halt the spread of Japanese Knotweed, warning signs identifying the plant have been erected by the Roads Department of Cavan County Council, which is leading the campaign locally to dissuade landowners and contractors from cutting the plant.
Alan Lyons, an engineer with the Roads Department, explained that they became involved in the fight against Japanese knotweed through piloting a particular chemical herbicide, Synero, on behalf of the National Roads Authority.
Whilst treating the weed on the county’s circa 200km of national roads, the council took the opportunity to also tackle the problem on Cavan’s 500km of regional roads. Firstly, council horticulturalist Bernie McGovern and her team conducted a survey in the summer to locate the plants.
They have located it at 20 sites on national roads and a further 42 on regional roads network and expect to spend €18,000 in treating it.
“It’s very easy to spot at this time of the year because of the flower on it,” Mr Lyons told the Celt. “It loses its leaf during winter, when it’s hard enough to spot.”
The Roads Department commenced the chemical treatment programme in recent weeks, as the herbicide is most effective when the plant is in bloom.
The council is conscious that landowners are obliged to ensure that hedges and trees on their properties are cut back and do not present a hazard to road users.
“The best thing to do, in our experience, is actually not to cut it, but kill it on-site with a chemical treatment,” explained Alan.
“As we go along the regional roads we decided to put up the signs - the signs are to stop hedgecutters from cutting it, because a hedgecutter may not know what he’s looking at, and this is the practical way of identifying them. They could be our contractors, or they could be a landowner’s contractors cutting the hedge - the sign is to notify both sides.”
The signs are also useful in marking the location for future treatments as Mr Lyons expects the council will have to repeat the treatment each September for three years.
As herbicides can be harmful to aquatic environments, where Japanese Knotweed occurs near water the council is using a special gun costing €400 to inject the chemical into the stem.
“The plant could have 50 or 60 stems,” Alan notes, “and you have to individually inject the chemical into the stem to kill the plant; now that’s a very time intensive process as you have to make sure you get every stem to kill it off.”
Japanese Knotweed grows at a staggering rate, reportedly up to 20cm every day, and can even burst through tarmac and concrete and undermine properties. To make matters worse, its roots can reach 3m deep.
It has presented a massive problem in the UK. Newspaper reports highlight family homes plummeting in value and property sales falling through if the merest trace of the plant is discovered. Annually it is costing the UK economy an estimated £166 million between treatments and in home devaluations.
Referring to the British experience, Alan observes, “The earlier we deal with it the less costly it will be”.
Given the Council’s modest resources, so far they have limited their eradication programme to regional and national roads.
“We still have to deal with the local roads and we have a very extensive road network, and we have to see how we’re going to plan that given the resources available,” said Alan.