A New Study Looked at the Long-term Environmental Impact of Various Japanese Knotweed Control Methods

A new study looked at the long-term environmental impact of various Japanese knotweed control methods.

Different approaches to controlling invasive species have evolved over time, but as sustainability becomes more important, understanding the impact of these management methods is critical.

This new study looks at the entire life cycle and long-term impacts of various management approaches.

The Environmental Cost Of Managing Japanese Knotweed

(Photo : David McNew/Getty Images)

It has been estimated that managing invasive species costs more than £165 million per year in the United Kingdom alone. Its presence can jeopardize home purchases across the country, as per ScienceDaily.

This has resulted in the development of various methods of attempting to control it; however, with sustainability becoming increasingly important, understanding the impact of these management methods is critical.

A new study, led by biosciences lecturer Dr. Sophie Hocking, has just been published in the online journal Scientific Reports, looking at the entire life cycle and long-term impacts of different management approaches.

"In light of the current climate emergency and biodiversity crisis, invasive species management and sustainability have never been more important," Dr. Hocking said.

Researchers know that invasive species can have significant negative ecological, social, and economic impacts, and the way we manage these species should mitigate this in a sustainable way to ensure we are not doing more harm than good.

Although more research has been conducted on how to best manage the plant, little is known about how sustainable these approaches are.

This study builds on previous research that has established Swansea University as a leader in Japanese knotweed expertise and understanding.

Professor Dan Eastwood and Dr. Dan Jones launched the world's largest knotweed control field trial in 2012, testing the species' main physical, chemical, and integrated control methods.

The study was carried out in collaboration with Complete Weed Control's Managing Director Ian Graham and Advanced Invasives, a spinout company led by Dr. Jones.

This field study was extremely beneficial to Dr. Hocking's work. A life cycle assessment (LCA) a methodology for assessing environmental impacts associated with all stages of a commercial process's life cycle was used to determine the relative environmental impacts of a variety of chemical and physiochemical knotweed management methods.

The researchers went beyond a focus on the use and end-of-life of these methods to assess the environmental impacts of various management methods, including the production of materials and herbicides required to achieve knotweed control; something that is frequently overlooked when evaluating sustainability.

The team chose common knotweed management methods for the study and used real-world data on time consumption, amount of materials used, and economic costs to assess their relative environmental impacts.

They discovered that the simplest approach glyphosate-based foliar spray control methods used the fewest materials, had the least environmental impact, and had the lowest economic costs, making it the most sustainable approach to knotweed management.

The findings are important for those who work with or are affected by the presence of Japanese knotweed on their property.

Also Read: Three Killer Plants Invaded the UK; What Are These Infamous Plants?

The Effects of Japanese Knotweed

Japanese knotweed spreads quickly, forming dense thickets that crowd out and shade out native plants. This reduces species diversity, changes natural ecosystems, and harms wildlife habitat, as per NYIS.

The ground beneath knotweed thickets has little other growth. This bare soil is prone to erosion, posing a particular risk to riparian areas.

Once established, Japanese knotweed populations are extremely persistent and difficult to eradicate.

Japanese knotweed, like most invasive plants, can colonize disturbed ecosystems quickly. One of the most effective ways to prevent knotweed colonization is to rehabilitate disturbed habitats with native vegetation before knotweed can invade.

Depending on soil conditions and root development, single young plants can be pulled by hand. Re-sprouting can occur if the entire root system is not removed.

Grubbing with a pulaski or similar tool to remove all of the roots after cutting back the standing vegetation can be an effective control measure for small initial populations beyond single plants, or in environmentally sensitive areas where herbicides cannot be used.

All plant parts should be bagged and disposed of in a secure location. Knotweed should not be mowed or cut with weed trimmers because the plant fragments can easily be moved around and re-sprout, spreading the plant rather than controlling it.

Herbicides such as glyphosate and triclopyr have been used to control Japanese knotweed.

Before using chemicals to control any invasive plant, consult your local environmental or natural resources management agency or Cooperative Extension office to determine which chemicals are legal to use on knotweed in your area.