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CABI providing sustainable solutions to Europe’s invasive weeds

www.cabi.org

KNOWLEDGE FOR LIFE

www.cabi.org

KNOWLEDGE FOR LIFE

CABI is a not-for-profit research organization with over 50 years’ experience in providing sustainable weed control. We are one of the few organizations in the world which works at a global level to provide long-term and sustainable invasive weed control.

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the problem of invasive weedsTrade and travel mean that exotic plant species are arriving in Europe at an ever increasing rate. A small but significant percentage of these plants become invasive. They are damaging our ecosystems and even human health, costing millions of Euros each year.

Areas affected:

Economic – Invasive weeds are costing Europe a fortune – both directly, through attempting to control them, and indirectly through lost resources and devaluing land. One of Europe’s worst weeds – Japanese knotweed – costs the UK alone more than €180 million a year. The cost of countrywide control, if attempted, would run to over €1.9 billion.

Safety – Invasive weeds can have severe impacts on human health, such as through allergenic pollen in the case of common ragweed (Ambrosia), or by toxic sap in the case of giant hogweed.

Biodiversity – Invasive weeds crowd out native vegetation and limit plant and animal species diversity. Some invasive plant species can reduce native plant richness by up to 90%.

Water quality and fisheries – Invasive weeds growing in and beside water bodies have the potential to alter food chains, and their impact on water quality can threaten aquatic ecosystems and fisheries. The presence of invasive weeds can seriously compromise the ecological status of a water body, and thus jeopardize the ability of Member States to comply with the Water Framework Directive.

Infrastructure – Invasive weeds can cause significant damage to buildings, drainage systems, railway lines, and other structures. This can add huge costs to development and regeneration schemes.

options for managing themDoing nothing – Invasive weeds will continue to have a devastating effect on native flora and fauna, damage the built environment and national economies, and affect people’s health.

Chemical control – Chemical herbicides can be effective where permitted, but using this method of control on a large scale is costly and could damage biodiversity. Many of the worst invaders are aquatic or grow beside rivers where use of chemicals is banned or severely limited.

Manual control – Manual control methods are available for most invasive weeds, but are rarely viable on large scale invasions because they are labour-intensive and costly.

Biological control – The only sustainable solution for many invasive species already out of control is the use of their own natural enemies (normally insects and pathogens) against them in what is known as classical biocontrol or biological control. ✓

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what is classical biocontrol?Classical biocontrol is the use of one or more of a plant’s natural enemies (insects, mites or pathogens) from its native range to suppress it permanently.

Over the past 100 years, more than 400 different biocontrol agents have been used against 150 target plants, totalling over 1,300 introductions around the globe.

Non-native species often become invasive because they have lost most (if not all) of their natural enemies in their translocation to new habitats. Of the many natural enemies keeping the plant in check in its native range, a few have evolved to become highly specific to their host plant, relying on it for food. It is these that classical biological control relies upon.

the biocontrol researchOur scientists study each invasive weed in its native range to identify the natural enemies that keep it under control. The research identifies which agents are specific to the plant, most damaging to the plant, and likely to flourish in the new environment.

Safety testing narrows the list of suitable natural enemies down to only those that are most likely to be safe in the plant’s new range, i.e. those that pose no threat to native vegetation and crops.

If the research reveals a suitable agent an extensive dossier needs to be prepared for consideration by the regulatory authorities who then decide whether to allow release of the insect or pathogen.

Once released and established, a successful biocontrol organism (called the “biocontrol agent”) will build up its population, causing an associated decline in the target weed’s population – but never eradication as that would remove its only food source.

CABI’s track recordCABI is a world leader in classical weed biocontrol. We have an international reputation for discovering and safety testing natural control agents, and helping governments to release them.

Over the past 50 years we have assisted over 35 countries in making releases of 75 species of insects and fungi against 30 weed targets.

Our 400 staff based in nine centres and offices around the world currently work in more than 60 countries, making us perfectly placed to research the natural enemies of invasive non-native species on a global level. Three specialist quarantine facilities in Europe allow us to work on any plant-feeding organism both legally and safely.

the safety issueFewer than 5% of released biocontrol agents have ever been recorded feeding on non-target species and all of these were either predicted to do so by the scientists at the time, or would be predicted under today’s rigorous pest risk analyses. A combination of literature reviews, field observations, and peer-reviewed experiments on feeding, egg-laying and development (or infection and sporulation in the case of fungi) are used today to ensure that the agent is safe.

Surprisingly, until recently there hadn’t been an officially sanctioned weed biocontrol release in any EU Member State, despite the long history of its use elsewhere.

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6 good reasons to use biocontrolEnvironmental – Biocontrol has an excellent track record in providing long-term control, especially for aquatic weeds. Properly resourced biocontrol programmes carried out to the highest standards have been very effective; as in Australia where the success rate is over 80%.

Biodiversity – Biocontrol specifically reduces the invasive weed without negatively affecting neighbouring native vegetation.

Cost – A review of cost:benefit ratios from over 30 weed biocontrol projects showed a range from 1:2.3 to 1:4000 with an average of around 1:200.

Sustainability – Biocontrol is permanent and therefore sustainable. The weed is continually under attack by the introduced natural enemies year on year.

Spread – Eventually the biocontrol agents will locate and affect most, if not all, populations of a weed until stopped by physical or environmental barriers, just as they have done in their native range. This means that currently inaccessible weed populations should still be controlled.

Safety – The selected biocontrol agents pose no threat to human health, crop production, or beneficial organisms.

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recent case studies

biocontrol of rubber vine in AustraliaRubber vine was introduced to Australia from Madagascar in the 19th century as an ornamental garden plant and as a source of latex. By the late 1980s, this aggressive climber, capable of smothering trees up to 40 metres high, infested over 40,000km2 and was described as the single biggest threat to natural and pastoral ecosystems in tropical Australia. Wide-scale chemical control was considered impractical, uneconomic and environmentally undesirable.

Surveys followed by extensive trials revealed a rust fungus, Maravalia cryptostegiae, to be safe and effective in controlling the weed. Aerial releases were made in 1995 and it is proving to be one of the most successful biological control programmes ever carried out against an alien invasive weed. The biocontrol agent is allowing native forests to regenerate and has provided a net value of at least AUD $232.5 million – a figure which grows year on year.

biocontrol of purple loosestrife in North AmericaPurple loosestrife (Lythrum salicaria) was introduced to the US and Canada from Europe as an ornamental plant. It has since invaded the natural environment, forming large stands, degrading many prime wetlands, and costing millions of dollars each year to control. The weed is now found in 48 US states where it crowds out native plant species. Once established, loosestrife stands are difficult and costly to remove by mechanical and chemical means.

To bring this weed under control, CABI scientists evaluated many of the more than 100 insect species that feed on purple loosestrife in its native European range. After extensive testing, six agents proved to be safe and releases in North America began in 1992. Of these, two leaf-eating beetles – Galerucella calmariensis and G. pusilla – proved to be particularly effective at controlling the invasive weed. As a result, this aggressive invader is now being successfully controlled in many wetlands. Up to 95% of purple loosestrife can be destroyed within two to five years of release – allowing native wetland plants to flourish once more.

release of Japanese knotweed psyllid in the UKThe CABI team has been working on the biological control of Japanese knotweed since 2000 and has tested the Japanese knotweed psyllid Aphalara itadori against 89 carefully selected plant species. In March 2010, based on this research, the UK government approved its release into the wild. This project not only promises to deliver a long-term control measure for one of the worst weeds in the world, but has also identified a suitable route from concept to licensing in a European Member State. The agent has now been released in parts of Great Britain, and a five-year monitoring programme is underway. This represents the first officially sanctioned release of an exotic weed biocontrol agent in any EU Member State and paves the way for further biocontrol releases in the near future.

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KNOWLEDGE FOR LIFE

find out morewww.cabi.org/biocontrol

contactDr Dick Shaw (English) E: r.shaw@cabi.org T: +44 (0)1491 829025

Dr Urs Schaffner (French & German) E: u.schaffner@cabi.org T: +41 (0)32 4214877

Dr Janny Vos (Dutch) E: j.vos@cabi.org T: +31 (0)33 4321031

KNOWLEDGE FOR LIFE