Superweed predator to be released in the UK

Rebecca Morelle, BBC News 9 Mar 10;

A tiny Japanese insect that could help the fight against an aggressive superweed has been given the go-ahead for a trial release in England.

Since Japanese knotweed was introduced to the UK it has rapidly spread, and the plant currently costs over £150m a year to control and clear.

But scientists say a natural predator in the weed's native home of Japan could also help to control it here.

The insect will initially be released in a handful of sites this spring.

This is the first time that biocontrol - the use of a "natural predator" to control a pest - has been used in the EU to fight a weed.

Wildlife Minister Huw Irranca-Davies said: "These tiny insects, which naturally prey on Japanese Knotweed, will help free local authorities and industry from the huge cost of treating and killing this devastating plant."

Alien invaders

Japanese knotweed was introduced to the UK by the Victorians as an ornamental plant, but it soon escaped from gardens and began its rampant spread throughout the UK.

It grows incredibly quickly - more than one metre a month - and rapidly swamps any other vegetation in its path.

It is so hardy that it can burst through tarmac and concrete, causing costly damage to pavements, roads and buildings.

But removal is difficult and expensive; new estimates suggest it costs the UK economy £150m a year.

However, in Japan, the plant is common but does not rage out of control like it does in the UK, thanks to the natural predators that keep it in check.

Scientists at Cabi - a not-for-profit agricultural research organisation - used this as their starting point to track down a potential knotweed solution.

They looked at the superweed's natural predators - nearly 200 species of plant-eating insects and about 40 species of fungi - with the aim of finding one with an appetite for Japanese knotweed and little else.

After testing their candidates on 90 different UK plant species, including plants closely related to Japanese knotweed such as bindweeds and important crops and ornamental species, they discovered a psyllid called Aphalara itadori was the best control agent.

The little insect feeds on the sap of the superweed, stunting its growth.

Dr Dick Shaw, the lead researcher on the project from Cabi, told BBC News: "Safety is our top priority. We are lucky that we do have an extremely specific agent - it just eats invasive knotweeds."

Following peer review by the Advisory Committee on Releases to the Environment and a public consultation, the UK government has now given the go-ahead for release of Aphalara itadori , under licence, in England.

The Welsh Assembly is expected to announce its decision on the psyllid soon.

The insects will initially be released on a handful of sites.

These will be isolated and, in addition to as having the superweed present, will also have UK species that are closely related to Japanese knotweed planted there to check that the psyllid only targets the invasive species.

Dr Shaw said: "In the early stages, a contingency plan is in place so that should, in the unlikely event, any unintended consequences be detected, we will be able to do something about it.

"Insecticide and herbicide treatment will be on standby for rapid response."

If this phase is successful, the insect will be released at further sites, where it will undergo an intensive monitoring programme over the next five years.

Dr Shaw said: "On the localised sites, I would expect to see damaged knotweed this season.

"However, biocontrol is a long-term strategy - it could take five to 10 years to have a real impact."

The government believes that if the plan is successful it will reduce the costs to the building and engineering industries of clearing the plant.

However, some critics say that it is impossible to be certain that the Japanese insect will only target the superweed and could attack other species once in the wild.


Hailing the arrival of alien predators
Matthew Cock, BBC Green Room 9 Mar 10;

Europe is about to release its first non-native "biological control" species to curb the spread of Japanese knotweed, and about time too, says scientist Dr Matthew Cock. In this week's Green Room, he sets out the case in favour of introducing natural predators to halt the march of invasive species.

For the first time in Europe, the UK government has granted approval for an insect from Japan to be released in order to control the invasive plant, Japanese knotweed.

It is the first time a "biological control" approach has been used in Europe against a plant.

But the concept is far from new, and Europe has been lagging behind other regions that have had more challenging experiences with invasive non-native species.

Japanese knotweed is a notorious plant, famed for its ability to burst through tarmac and crack concrete. Just finding it on a development site can result in huge additional costs or force developers to find alternative sites.

There have even been reports of mortgage companies refusing to lend to house buyers whose dream homes have Japanese knotweed in the garden.

In contrast, in its native range in Japan, it is just another member of the Japanese flora and it is fed upon by over 200 natural enemies, mostly plant-eating insects and plant diseases.

It is amongst these natural enemies that scientists believe the answer lies.

Counting the cost

Alien plants in the UK cost a vast amount of money and this expenditure, like the plants themselves, tends to expand at an ever-increasing rate.

It has been estimated that to manage Japanese knotweed in the UK, without successful biological control, would leave farmers, gardeners and local councils facing a bill of at least £13.5bn ($20.4bn; 15bn euros) by the end of the century.

This does not include the less obvious costs to the environment and those species that are displaced by these invaders.

The rate at which new plant invasions are happening is accelerating, as a result of factors such as increasingly mobile human populations, larger volumes of traded goods and climate change, all of which make it easier for plants to reach new areas.

Europe needs to find new ways to combat the most damaging species that become established.

The majority of these newcomers arrive without their natural enemies that can keep them in check in their native range, and this may give the exotic plants a great advantage over their new neighbours.

Biological control - the use of living organisms to control pest populations - can be thought of as a means of levelling the playing field by introducing some of the specialist natural enemies that exert control on the pests in their native range.

However, this can only be done with extreme care.

Safety first

I am an environmental scientist. The first question I ask before proposing to import a new organism is: "Is it safe?"

Worldwide, there have been more than 7,000 introductions of biological control agents to date, about 1,300 of which were for weed biological control. The remainder was for control of invertebrate pests, mostly insects.

Of the 1,300 releases against weeds, more than 400 different agents have been released against more than 150 different target weeds over the last 110 years. Of these, only nine produced any collateral damage such as feeding on native species.

I imagine that some readers will be asking: "What about the cane toad?"

The cane toad was introduced into Australia from South America by the sugar cane industry in 1935 because it was known to eat some of the most important sugar cane pests.

There was no consideration of what the potential food range would be, or what impact the cane toads might have on the native fauna.

Not surprisingly, the toads - which grow to 20cm (8in) - turned their carnivorous attention to anything that moved. They will eat anything that they can get into their mouths.

The toads went on to become a significant problem, having a detrimental effect on native fauna, including amphibians and reptiles, as well as poisoning domestic and wild animals that tried to eat them.

Today's practitioners of biological control consider this release an ecological disaster, but one which demonstrates very clearly what can happen when a generalist predator is introduced without considering the risks that they present to species other than the target pests.

Those who regulate the introduction of biological control agents have learnt this lesson.

The methodology of science and predictability of introducing an exotic insect or plant disease for biological control has improved greatly, so that tests carried out by scientists allow good predictions to be made of what will happen in terms of safety when a weed biological control agent is introduced.

No introduction of an exotic organism can be entirely risk free, but the risk of a highly studied, specialist natural enemy feeding outside its experimentally evaluated host plant range is extremely low.

Overall, the safety record of weed biological control has been exemplary and the beneficial impact has been enormous.

Making up lost time

In the last 50 years, five countries have led the world in implementing successful weed biological control: Australia, Canada, New Zealand, South Africa and the US.

In countries like these, research into biological control is always considered and often prioritised when a new and problematic invasive plant species get out of hand.

Between them, they have tackled more than 100 weeds and achieved partial or substantial control of more than 50, with at least 30 programmes active at the moment and too early to judge.

To give just one example, the alien invasive rubber vine weed was successfully brought under control in Australia.

Introduced from Madagascar in the 19th Century, this aggressive climber was considered the single biggest threat to natural ecosystems in tropical Australia.

By the late 1980s, infestations were vast, covering 40,000 square kilometres. A rust fungus, Maravalia cryptostegiae was identified as a highly promising biological control agent and after extensive trials to assess it safety, aerial releases were made in Australia in 1995.

It is promising to be one of the most successful biological control programmes ever carried out, with heavy damage to the weed allowing regeneration of native forests. It was estimated to have provided a net value of £140m by 2005 - a saving that is growing year on year.

The UK's Department for Environment, Food and Rural Affairs (Defra) decision to grant a licence to release a biological control agent for Japanese knotweed is a milestone decision for Europe that will open the way to assess the scope for biological control of other alien weeds such as floating pennywort and Himalayan balsam, themselves very obvious and damaging invaders.

Europe can now start to catch up with the rest of the world and gain the benefits of sustainable, environmentally safe biological control of some of its most environmentally damaging alien invasive weeds.

Dr Matthew Cock is chief scientist for Cabi, a not-for-profit science-based development and information organisation

The Green Room is a series of opinion articles on environmental topics running weekly on the BBC News website

What is the psyllid?
Millions of sap-sucking insects are to be introduced to control Japanese knotweed. But what kind of insect is the new gardener's friend?
Louise Gray, The Telegraph 9 Mar 10;

The psyllid is the name given to a whole family of jumping plant lice that are found all over the world. But the different species tend to be very "host specific" meaning they will only eat one type of plant.

This makes them very useful in biocontrol because they can be released to kill one type of plant without affecting other wildlife.

The psyllid Aphalara itadori, to be released in Britain, only eats Japanese knotweed. The insects were brought to the UK from a specific location in southern Japan where the plant grows on rocky volcanic slopes and the climate is similar to the UK.

The aphid-like insect is about 2mm long and is an orange or brown colour. Typically the psyllid will only live for a few weeks and go through two or three life cycles in one summer. It lays thousands of eggs which hatch and immediately start sucking sap from the plant through its sharp mouth.

The winged insects are currently being bred in captivity in Britain but could spread once they are released, using the wind to carry them further.

However psyllid will be eaten by native predators like spiders and wasps and should die out once Japanese knotweed is brought under control.

Cabi, the not-for-profit organisation that is rolling out the introduction of the psyllid, put eggs on around 90 other plants like the knotweed but none were able to develop as adults.

They concluded that this made the species the "perfect candidate" for the first release of a non-native species to control another pest.

Plantlife, the plant charity, has suggested that three additional plants (Northern Knotgrass, Tasteless Water-pepper and Small Water-pepper should also be tested prior to release amid concerns the psyllid may affect these species.