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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

 

Controlling the cabbage seedpod weevil in Canada

The cabbage seedpod weevil is a widely distributed pest of cruciferous crops in Europe and North America, causing substantial economic losses in canola crops in Canada. Current control measures still rely on applying broad-spectrum insecticides. We are collecting European distribution data for a parasitic wasp that is the weevil’s most effective... >>

Biological control of brown marmorated stink bug

The brown marmorated stink bug is native to parts of East Asia and is invasive in the US, Canada and Switzerland. Here, it is a serious pest of many fruit trees, shrubs and other plants. Chemical control is often used but, with testing, parasitic wasps from China could be used in North America instead. So we want to determine what natural enemies... >>

Controlling earwigs in the Falklands

The European earwig has become a considerable domestic and public nuisance in the Falkland Islands, causing significant problems for local horticulture by decimating many garden vegetable crops. This population explosion is due to the absence of natural enemies that would normally keep them under control. To try and find a solution to this... >>

Controlling the noxious Russian knapweed in North America

Although native to Asia, Russian knapweed was accidentally introduced to North America over 100 years ago and is now causing untold problems across many states. Some decades ago, a nematode species was used in an effort to control the plant but it proved ineffective. Funded by a US and Canadian consortium CABI has been tasked with researching and... >>

Locating a biological control for tutsan in New Zealand

Tutsan, native to Europe, was introduced to New Zealand but is now a major invasive species. In 2011, CABI’s Swiss centre was approached by Landcare Research to investigate prospects for the biological control of tutsan. Surveys in the native range revealed a suite of insects and pathogens. CABI’s laboratories in the UK are currently conducting... >>

Azolla control

One of the UK’s most invasive plants, the fairy fern or floating water fern causes problems for anglers and water managers. It forms thick mats on the water’s surface which can double in size in a few days, blocking out light and killing aquatic flora and fish. Fragmentation of the fronds makes control by mechanical means virtually impossible.... >>

Assessing the impacts of coffee green scale in Papua New Guinea

Almost 90% of Papua New Guinea’s coffee production is supplied by highland smallholder farmers who own less than half a hectare of land and have limited resources. Coffee green scale is a serious pest. Through undertaking regular surveys, this project will build a better understanding of the impact of the pest on the crop yields of smallholders... >>