Knocking back knotweed in Kerry

SIR, An intense couple of months treating Japanese knotweed has just come to an end for RaptorLIFE – a €3 million EU LIFE conservation project at IRD 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 6500m2 covering 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. While this is a great start, they will have to repeat it all again for the next few years as knotweed is an incredibly resilient weed.

IRD Duhallow are targeting Japanese knotweed because it is a widespread invasive species. Invasive species are plants, fungi or animals that are not native to a specific location (an introduced species), which spread and can damage the environment, economy, or human health. 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.

While knotweed does not 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. For example, 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 is tackling some of the worst invasive species that degrade ecosystems and impact the local communities 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.

The best way to fight invasive species is to prevent them from occurring 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. There are many non-invasive alternatives so please replace invasive plants in your garden with non-inv asive alternatives. Ask your local garden centre staff for help when choosing alternative non-invasive plants for your garden. Sincerely, Dr. Ilse Corkery, RaptorLIFE Project Scientist, I.R.D. Duhallow Ltd., James O’Keeffe Institute, Newmarket, Co. Cork.

Photo by Nuala Riordan Spraying knotweed on the roads and Duhallow.