The Japanese Knotweed

Insect to be released to control the Japanese Knotweed

The Department for the Environment, Food and Rural Affairs, along with the Welsh Assembly Government, are considering a proposal to release an insect into the wild to help control the Japanese Knotweed (Fallopia Japonica).

The Japanese Knotweed is a large herbaceous perennial plant that has hollow stems with distinct raised nodes and small creamy white flowers that is native to Japan, China and Korea. The species is now very prominent in North America and Europe and you will often see it sprouting through cracks in the pavement. It’s no wonder that something needs to be done to help tackle this weed as it has been listed as one of the world’s 100 worst invasive species in the World Conservation Union, as it forms thick dense colonies that completely crowd out other herbaceous species.

The idea is that the non-native Psyllid Alphalara Itadori, which is a sap-sucking insect, will weaken plants and make them easier to remove through everyday gardening and more vulnerable to herbicide treatments.

In the long term they hope to save an estimated £1.56 billion that it cost to eradicate unwanted plants in 2003.

Over 150 organisations are being asked for their opinions and a decision is to be made by the 19th of October 2009. If the proposal is put into action the insect will be released into a small number of areas and strictly observed by two regulatory processes. The release of non-native bio-control agents is controlled under the Wildlife and Countryside Act 1981 which also made the spread of this plant illegal.

There are also restrictions on the import and release of non-native plant pests under the Plant Health Order 2005, so there’s no need to worry, if the insect isn’t having a positive affect we will soon know about it.

Updates

The Government has now given the go-ahead for the release of Alphalara Itadori, under licence, in England. The insect will be released in a handful of sites this spring; this will be the first time that bio control (the use of a natural predator to control a pest) has been used in the EU to fight a weed.

The lead researcher from the project, Dr Shaw, has stated, “safety is our top priority, we are lucky that we do have an extremely specific agent that just eats invasive knotweeds”. Some critics are concerned as to how they can be so sure it will not attack other species in the wild.

Dr Shaw predicts; "On localised sites, I would expect to see damaged knotweed this season. However, bio control is a long-term strategy – it could take five to 10 years to have a real impact".

The government hopes, that if the scheme is successful, the current costs of clearing the plant will be dramatically reduced.

Here at the Gardeners Club we will continue to keep you updated on any further developments on this interesting topic.