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Improving lives by solving problems in agriculture and the environment

Biological control of invasive species: case study

Biological control of invasive species: case study

Non-native invasive species are extremely detrimental to livihoods, biodiversity and food production wordwide. Biological control methods provide a sustainable and cost-effective solution to Invasive Alien Species (IAS) that minimizes the use of pesticides.

Damaged plants

Safeguarding the environment, food security and livelihoods from invasive species using biological controls 

Non-native invasive species, such as insect pests and weeds, have a huge impact on livelihoods, food production and biodiversity around the world. We tackle this issue by using classical biological control which provides a sustainable and cost-effective control method and minimizes the use of pesticides. In this case study, we outline three examples from programmes where CABI scientists have played a role, and provide results from a further five studies.

Rubber vine

Rust pathogon decreases rubbervine by up to 90%

Rubbervine is native to South West Madagascar but was introduced to Queensland, Australia in the 1860s. in just over a century it has spread over 34 million hectares wreaking havoc on its ecosystem. CABI scientists were able to find a rust pathagon which acted as a control agent and reduced the weed by up to 90% in some areas. This allowed for more cattle production and reduced the costs of weed control. This finding has also benefitted places like Eastern and Southern Africa, Brazil, Mexico and Cuba who are all experiencing rubbervine problems.

Mealybug on a Mango plant

Intervention leads to benefit of $531 million

The mango market in Benin was valued at US $65 million per year. In the 1980s the mango mealybug invaded from South East Asia and by the 1990s had caused an 89% decrease in yield. CABI scientists found two parasitic wasps which, once released and established, managed to control the mealy bug population. This resulted in fruit production levels increasing dramatically. The benefits of biocontrol in Benin have been estimated at US $531 million.

cassava mealy bug

Mealybug causing crop losses of up to 80%  

While cassava is actually native to South America, it has become an important staple in tropical Africa. It is grown by many low income farmers and provides both food security and income. In the 1970s the cassava mealybug population erupted and spread rapidly, mainly due to it not having any natural enemies. The impact was devestating as it compromised food secuity for over 200 million people.

Through research, it was found that a parasitic wasp native to areas such a Bolivia and Brazil fed on the mealybugs. It was introduced to Africa and within a decade had reduced the mealybug population by 95%.

It is widely known that invasive species are tackled more in developed countries than in developing countries. This means that there is a huge need for biocontrol research in developing countries to protect people from the threats of food security and income that arise from the invasion of non-native species.

CABI is working in Africa and Asia to try and manage invasive species in order to optimize food production and support farmers.

 

The need for effective biocontrol methods in developing countries is emphazised by the success of biocontrol projects in developed countries, such as the UK.

Japanese knotweed has been described as one of the worst invasive species in the UK as it is extememly hard to control and can cause extensive structural damage to buildings, roads and carparks. It was estimated that it would cost the UK Government £1.56 billion were control to be attempted country-wide in the UK. But a CABI-led project investigating the biological control of Japanese knotweed unearthed a psyllid that feeds soley on Japanese knotweed and should significantly reduce the cost of controlling the non-native species. It was released in 2010 as part of a phased release and is being monitored. Further efforts to increase the population in the field are ongoing.

Himalayan balsam is quickly becoming one of the UK's most invasive species. It grows rapidly in wetland conditions, compromizing biodiversity as well as flood defenses.

It has quickly spread out of control due to a lack of native predators, this suggested the need for a biocontrol mechanism to remedy the effects of the Himalayan balsam invasion.

CABI scientists have found a new type of rust fungus that spreads through infestations of the weed. The rust completes it's entire five-stage life cycle on a single species, causing infection to the stem and leaf of the plant during growing season.

See a video that we have produced on the weed and our research

 

Protecting leeks and onions from pests

The invasive leek moth poses a significant and immediate threat to producers of leeks, onions, garlic and chives in North America. The larvae mine the green tissues, reducing the marketability of crops. The pest’s distribution is expanding, with no signs of suppression by indigenous natural enemies. We are supporting an integrated pest management... >>

Biological control of brown marmorated stink bug

International trade is a common way for insects to ‘hitch-hike’ their way to new countries. The brown marmorated stink bug, originally from East Asia, has become a harmful invasive pest of many fruit and vegetable crops in North America and Europe. Biological control using Asian or European natural enemies may be an environmentally friendly,... >>

Biological control of garlic mustard

Crushed garlic mustard leaves and seeds smell like cultivated garlic and have been used as flavouring in cooking for centuries. Garlic mustard is a brassica from Eurasia that was accidentally taken to North America and became invasive in many of its forests. Together with partners, CABI is exploring the possibility of using specially selected and... >>