Insect and fungi to tackle knotweed in Wales

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Japanese knotweed
Image caption,
Japanese knotweed growing next to the River Taff in Cardiff

Two projects running in Wales are trying to check the spread of the invasive plant Japanese knotweed.

One run by the University of Glamorgan is mapping the plant's spread with satellite technology, and looking at using native fungi to attack it.

The other sees a Japanese insect, which preys on the plant, being released, with Swansea the likely location.

The plant costs millions each year to eradicate, with councils, householders and businesses footing the bill.

It grows rapidly and can break through hard surfaces, causing structural damage to properties.

Nowhere has been more linked to the problematic plant than Swansea, which has been dubbed "knotweed capital" due to its prevalence in the area.

Swansea council even went as far as to employ a "knotweed officer" in its environment department, one of whose main duties was to tackle the problem in the city.

The amount of the plant present - estimated to be 62,000 tonnes - made it the probable location of one of a number of trial sites where the psyllid insect is being released in the UK in an attempt to contain the plant's growth.

The exact locations, either two or three in the UK, are being kept secret by the Centre for Agricultural Bioscience International, the organisation running the trials.

At the University of Glamorgan near Pontypridd, head of biology research Professor Denis Murphy is leading work on developing satellite technology to image knotweed from above.

He said: "We won't need people on the ground walking around identifying it.

"It's particularly useful looking at its spread. We have submitted that for publication and we're hoping that system's being adopted.

"We're also looking at the biology of knotweed and why it's able to spread so easily.

"One of the things seem to be that it's resistant to a lot of the diseases that attack other plants.

"We have detailed a couple of fungi that may work. If they really do attack the plant we could use it in the future."

Professor Murphy said their research suggested the plant seemed to grow very easily in poor soil.

"It makes the soil even poorer, so other plants can't compete with it. It seems to stop animals getting into the soil and other plants growing so the soil becomes impoverished," he explained.

Alien species

"It really sets up its own ecosystem."

The team are cautious about the Cabi project involving the psyllid insect as it means importing yet another alien species to the UK.

"We're a bit concerned that it could start attacking other plants so we'd rather use something which is native," Professor Murphy said.

Asked why the native fungi being investigated had not already started attacking knotweed, he said the plant was only introduced to the UK at the start of the 19th Century which in evolutionary terms was "nothing".

The fungi are also not likely to be in close proximity to the places where knotweed grows.

'Widespread consultation'

The project would look to give nature a helping hand by introducing a fungus directly to the plant.

He added: "The fungus will probably eventually start attacking knotweed but it could take 400 years. We don't want to wait that long."

Djamila Djeddour from the Cabi knotweed team said there had been widespread consultation over the safety of the psyllid and the research had been peer-reviewed prior to the trials beginning.

"The science has shown the insect to be a knotweed specialist and we have undertaken years of research to assess safety and highlight any potential risks to non-target plants," she added.

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