Invasive Species
In the U.S. and Europe, Japanese knotweed is widely considered an invasive species or weed. It is listed by the World Conservation Union as one of the world's 100 worst invasive species.
The invasive root system and strong growth can damage concrete foundations, buildings, flood defences, roads, paving, retaining walls and architectural sites. It can also reduce the capacity of channels in flood defenses to carry water.
It is a frequent colonizer of temperate riparian ecosystems, roadsides and waste places. It forms thick, dense colonies that completely crowd out any other herbaceous species and is now considered one of the worst invasive exotics in parts of the eastern United States. The success of the species has been partially attributed to its tolerance of a very wide range of soil types, pH and salinity. Its rhizomes can survive temperatures of −35 °C (−31 °F) and can extend 7 metres (23 ft) horizontally and 3 metres (9.8 ft) deep, making removal by excavation extremely difficult. The plant is also resilient to cutting, vigorously re-sprouting from the roots. The most effective method of control is by herbicide application close to the flowering stage in late summer or autumn. In some cases it is possible to eradicate Japanese knotweed in one growing season using only herbicides. Trials in the Queen Charlotte Islands (Haida Gwaii) of British Columbia using sea water sprayed on the foliage have demonstrated promising results, which may prove to be a viable option for eradication where concerns over herbicide application are too great.
It can be found in 39 of the 50 United States and in six provinces in Canada. It is listed as an invasive weed in Ohio, Vermont, Virginia, West Virginia, New York, Alaska, Pennsylvania, Oregon and Washington state. The species is also common in Europe. In the UK it was made illegal to spread Japanese knotweed by the Wildlife and Countryside Act 1981. It is also classed as "controlled waste" in Britain under part 2 of the Environmental Protection Act 1990. This requires disposal at licensed landfill sites.
Two biological pest control agents that show promise in the control of the plant are the psyllid Aphalara itadori and a leaf spot fungus from genus Mycosphaerella.
Read more about this topic: Japanese Knotweed
Famous quotes containing the words invasive and/or species:
“The frequency of personal questions grows in direct proportion to your increasing girth. . . . No one would ask a man such a personally invasive question as “Is your wife having natural childbirth or is she planning to be knocked out?” But someone might ask that of you. No matter how much you wish for privacy, your pregnancy is a public event to which everyone feels invited.”
—Jean Marzollo (20th century)
“Any reading not of a vicious species must be a good substitute for the amusements too apt to fill up the leisure of the labouring classes.”
—James Madison (1751–1836)