It may look beautiful but Japanese knotweed is proving to be a major environmental headache in both Cork and Kerry. However, help is at hand as Dr Ilse Corkery, RaptorLIFE Project Scientist at IRD Duhallow has, with her team completed an intense couple of months treating Japanese knotweed in Duhallow.
As part of their work, “Do not cut” signs were erected throughout Duhallow including roads in Kerry, which are within the project area of the upper Blackwater catchment and the Mullaghereiks SPA (Special Protected Area).
On Kerry roads alone they have sprayed stands totalling well over 58km of road verge. On the Upper Blackwater River, they treated 137 stands, using the direct injection method and covered 10km of riverbank.
But as Dr Corkery pointed out that while this is a great start, they will have to repeat it all again for the next few years as Japanese knotweed is an incredibly resilient weed.
To showcase its resiliance, at its most prolific knotweed can grow up to 20cm a day, and can even grow through concrete and tarmac with its roots growing down to 3m deep. With no natural enemies the weed can grow unabated, swamping other plants and preventing them from getting any light.
As Dr Corkery outlined, while the Japanese knotweed doesn't produce seeds it can grow from small fragments of rhizomes – the underground network of stems and roots – meaning it spreads easily. If left unchecked, knotweed can degrade local ecosystems and devalue property.
She pointed out that knotweed costs the UK economy an estimated €186 million per year for treatment and home devaluations. As knotweed will spread from small fragments, the best method to control it is the application of a glyphosate herbicide (Roundup) during September when the plant is actively drawing nutrients back down from its leaves into the root network.
IRD Duhallow has been working on controlling invasive species for a number of years. Through a selection of different sustainable techniques such as manual removal and careful application of herbicide, IRD Duhallow’s RaptorLIFE project, which is a €3 million euro project, is tackling some of the worst invasive species that degrade ecosystems and impact the local community who depend on these ecosystems for the environmental services they provide. "Rural development and sustainable agriculture is at the core of the RaptorLIFE project, and raising awareness on ways to prevent the arrival and spread of invasive species is a priority" Dr Corkery.
She said the best way to fight invasive species is to halt them in their tracks in the first place. "The public can help stop the introduction and spread of invasive plants by checking that the plants they buy for their garden are not listed by Invasive Species Ireland as a problem" she said.
