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Controlling Japanese Knotweed in your garden

Japanese KnotweedWhen you are involved with weed control, you will always get asked about a wide range of weeds that can appear in a garden, even though your specialist knowledge is really lawn weeds. Being the helpful sort, we like to keep you up to date with all weed related matters and this technical post is about controlling Japanese Knotweed and provides some up to date news about this invasive weed.

Defra is seeking the public's views on the introduction of Japanese-knotweed-eating insect Aphalara itadoria to the UK to help control Japanese knotweed. Research Scientists have identified an insect that keeps the superweed under control in its native home of Japan and think it could do the same in Britain. If the plan gets the go-ahead, the insect could be released next summer. This would be the first time that biocontrol - the use of a natural enemy to control another pest - has been used in Europe to fight a weed. The release would initially take place at a small number of sites before a wider introduction in England and Wales.

The Government is considering an application for a licence to release the psyllid at a small number of sites to begin with, eventually rolling out across England and Wales, after research found the psyllid is unlikely to eat native plants as well.

CABI research head Dr Dick Shaw said: "In the case of Japanese knotweed, doing nothing is not an option, so we are applying a century-old technique to a new target and are very hopeful of an effective and sustainable outcome."

Japanese knotweed is native to Japan, Taiwan and China, and was introduced to Europe as an ornamental plant in the early 19th century. It is a large vigorous weed that appears to have no natural enemies in Britain. It can colonise most habitats and is regarded as a troublesome pest in many parts of the country because of its rapid invasion and domination of habitats, which results in the exclusion of other plants. It can damage property (for example by growing through tarmac or even the floors of houses) and therefore needs to be cleared from development sites. The species also causes problems in terms of flood management. It increases the risk of riverbank erosion when the dense growth of the plant dies back in the autumn exposing bare soil. It can also create a flooding hazard if the dead stems are washed into the streams and clog up the channel. A fragment of root as small as 0.8 grams can grow to form a new plant. Eradicating the plant using conventional methods was estimated at £1.56bn in 2003.

Defra said insect is "effective and environment-friendly". Defra stands for Department for Environment, Food and Rural Affairs.

If you are a land owner and you have Japanese Knotweed on your lawn, you must control the weed and also take adequate precautions in the disposal of the treated but dead vegetation so as to contain the spread of the weed. You can read more about eradication methods here.

The Environment Agency has drafted a Japanese Knotweed Code of Practice to help land and home owners who have the weed on their land.

Credits - BBC & Horticulture Week

“Photograph Copyright Environet Consulting Ltd – reproduced with their kind permission”


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