A fifth of the world’s plants under threat, as report says 391,000 species now known to science

Dave Simpson – 11 May 2016

A ground-breaking report from the Royal Botanic Gardens, Kew, has produced an estimate of the number of plants known to science. By searching through existing databases, the researchers have estimated that there are now 390,900 known plant species, of which around 369,400 are flowering plants. But this figure is only those species currently documented: new species are being discovered all the time, including over 2000 in 2015 alone. But more worryingly, it is suggested that 21% of plant species are under threat, from a range of pressures including climate change, habitat loss and invasive species. The invasive species component of the report, which draws heavily on CABI’s Invasive Species Compendium, says that nearly 5,000 plant species are documented as invasive, from over 13,000 vascular plant species naturalised outside their native range.

Prof Kathy Willis, director of science at RBG Kew, said: “It’s really important to know how many plant species there are, where they are and the relationship between the groups, because plants are absolutely fundamental to our well-being”

And on invasive species, the head of conservation science at Kew, Dr Colin Clubbe, said that invasive species are one of the biggest challenges for biodiversity. Quantifying the number of species regarded as invasive is a key step towards addressing the problem. “Now that we’ve got this list and this number, it’s certainly a bit like know your enemy,” said Dr Clubbe.

JK

Japanese knotweed, a major invasive
“We know what we are dealing with, we can then look at them, and see what’s similar, what makes a good invasive, and then see how we can use that information to have better management practices in place or recommendations for how you deal with them.”

 
Trade, plant collecting, and movement of people, has led to at least 13,168 species of vascular plants becoming naturalised outside their native range. The report says that they become classed as invasives once they start to compete with native vegetation and spread to a degree that causes damage to the environment, the human economy or human health. The effects on livelihoods, and on ecosystem services such as agriculture, forestry, water and pollinators, can be staggering: the Kew report cites one study as estimating the total costs from all invasive species as nearly 5% of the world economy, and it also quotes CABI research which estimated the impact on the British economy alone as around £1.7 billion every year. Japanese knotweed, one of the most invasive plants in the UK, costs Great Britain over £165 million annually to control.

The Kew report synthesizes invasive species data from the open-access CABI Invasive Species Compendium, the Global Invasive Species Database (GISD), global reviews of invasive trees and shrubs by Rejmánek and Richardson, and Weber’s Invasive Plant Species of the World: a Reference Guide to Environmental Weeds published by CABI in 2003. CABI’s ISC – flagged in the report as “the most comprehensive web-based resource” – has datasheets for 4,841 of the total of 4979 invasive vascular plants in Kew’s consolidated list.

Identifying other threats to plant biodiversity, the report says that farming is the biggest extinction threat, representing 31% of total risk to plants. Logging and the gathering of plants from the wild is responsible for 21.3% of the risk, followed by construction work with 12.8%. The report said that some 1,771 areas of the world have been identified as “important plant areas” but very few have conservation protection measures in place.

Highlighting just how many plant species are already important to humans, the report says that some 17,810 plant species have a medical use, 5,538 are eaten, 3,649 become animal feed and 1,621 are used for fuels. Over 11,000 plant species are used for materials, for example fibres and timber.

“[Plants] provide us with our food, our fuel, our medicines – even controlling our climate” says Professor Willis.

The report can be downloaded in full, or data from individual sections accessed, at the website stateoftheworldplants.com. A symposium on the report is being held at Kew on 11-12 May. Moving forward, the global assessment will now be carried out annually, allowing scientists to monitor how plants are changing over time.

Malaria incidence and invasive plants – is there a link?

Mosquito

25 April is World Malaria Day – a time to reflect on the steps we can take to tackle this terrible disease. Much progress has been made in the fight against malaria over the past 15 years, like the use of bed nets impregnated with pesticides, but 3.2 billion people are still at risk. If we are to achieve a 90% reduction in global malaria incidence and mortality by 2030 we must do more.

The path will not be easy. Mosquitoes are becoming increasingly resistant to pesticides – the front line of defence from malaria today. But there are other aspects we can consider, like the potential link between the incidence of malaria and invasive, non-native weeds.

It is widely known that mosquitoes need plant sugars, among other things, to survive and proliferate. Studies in Israel show that mosquitoes are much more likely (250 times more likely) to transmit malaria in areas rich in plant sugars. Could the improved management of invasive plants abundant on the African continent lead to a reduction in the incidence of malaria?

It is this question that brought together experts on malaria and plant invasions to a workshop in Kenya in December 2015, funded by the Bill & Melinda Gates Foundation. The broad objective of the workshop was to explore whether mosquitos benefit from invasive plants and whether these plants have a positive influence on the rate of malaria transmission. The workshop also looked at whether invasive plants could be managed on a large scale.

Experts agreed that access to particular plant sugars increases the ability of Anopheles mosquitoes to transmit malaria. Although it is not known if invasive plants produce more sugars, they are more widespread and abundant than native plant species. In fact, many have the ability to invade semi-arid and arid areas, possibly increasing the prevalence of malaria in regions where mosquitoes could not survive in the past. Invasive plants also actively grow and produce flowers and fruit for longer periods than native plants, thereby extending the availability of plant sugars over longer periods than in the past. This may allow mosquitoes to retain high population numbers for much longer periods in invaded areas than in areas where there are no suitable invasive plants.

If there is an obvious link between invasive or weedy plants andAnopheles mosquitoes, can we significantly reduce the incidence of malaria by managing invasive plants?

There is no doubt that problematic plants can be controlled. Landowners, especially farmers, do it all time. The Government of South Africa allocates approximately US$120 million a year to control invasive plants, especially in water catchments, biodiversity hotspots and protected areas. It also invests in biological or natural control of invasive species. This is considered one of the most cost-effective management options, ideal for use in developing countries that do not necessarily have the resources for chemical or conventional control.

So, we can control weeds but would it reduce the incidence of malaria?

Lowering the abundance and density of any plant species favoured by Anopheles mosquitoes should lower malaria incidence. Managing many of these non-native weeds will also result in a multitude of other benefits for poor rural communities – like protecting farmland, for example.

This possible malaria-invasives linkage must be explored further. We need to do more research to fill in knowledge gaps. This includes looking at what plant species the Anophelesmosquitoes use within a given environment. Methodologies are being developed to see if rapid assessments of mosquito gut contents can provide information on what plant species they have been feeding on. We also need to look at the impact of removing certain species of invasive plants on mosquitoes. If we can compare mosquito abundance, longevity and ability to transmit malaria in areas where the invasive plant is dominant and where it is less dominant, we can build a fuller picture of the potential problem and solution.

Malaria is a terrible disease that still affects too many people. We must do all we can to understand the possible link between the incidence of malaria and invasive, non-native weeds. If a link can be found, management of invasive weeds could offer hope to many living under the threat of malaria.

By Dr Arne Witt, Coordinator, Invasive Species, CABI

For more information about CABI’s work managing invasive species, click here.

New in January and February 2016 from the ISC

In January and February 2016 the following datasheets were published on CABI’s Invasive Species Compendium (ISC). You can explore the open-access ISC here: www.cabi.org/isc.

By Franz Xaver (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0) or GFDL (http://www.gnu.org/copyleft/fdl.html)], via Wikimedia Commons

1. Agropyron cristatum

Agropyron cristatum (crested wheatgrass)

A. cristatum is a resilient and long-lived perennial grass with stems that are 20-70 cm long and with finely-branched deep roots that extend to a depth of 1 m. It is able to grow in a wide range of habitats making it a very effective invader. Its native range is the Russian and Siberian steppes but it is now present in the North American prairies where it was planted in the 20th century to reseed abandoned cropland. It has since invaded vast areas of rangeland across the upper USA and southern Canada where it outcompetes native vegetation, altering soil chemical properties as a result.

By Homer Edward Price (Bushy-Bluestem Uploaded by Amada44) [CC BY 2.0 (http://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons

2. Andropogon glomeratus

Andropogon glomeratus (bushy bluestem)

A. glomeratus is another invasive perennial grass, but is taller than A. cristatum, with stems that can be 1.5 m in height. It is a popular ornamental because of its bushy/tufted appearance and is consequently found outside of its native range of southeastern USA, Mexico and parts of Central Mexico and the Caribbean. Introduced to Hawaii, USA, where it is considered a noxious weed, it is outcompeting the small, native and endemic shrub Vaccinium reticulatum. A. glomeratus can also change fire regimes as it is highly flammable. This can promote invasion by other non-native species.

By scott.zona (Flickr: Atriplex semibaccata) [CC BY 2.0 (http://creativecommons.org/licenses/by/2.0)], via Wikimedia Commons

3. Atriplex semibaccata

Atriplex semibaccat (Australian saltbush)

A. semibaccata is a perennial shrub which can grow up to 80 cm tall and is drought and salt-tolerant. It is a valued fodder crop but it can form dense and fire retardant groundcover that displaces native species. In Hawaii, USA, it is impacting on a number of endangered plants such as Panicum niihauense, along with other invasive species. In California, USA, it is competing with Verbesina dissita which is endangered and restricted to the Laguna Beach area of Orange County.

I, Hugo.arg [GFDL (http://www.gnu.org/copyleft/fdl.html), CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/) or CC BY-SA 2.5-2.0-1.0 (http://creativecommons.org/licenses/by-sa/2.5-2.0-1.0)], via Wikimedia Commons

4. Phleum pratense

Phleum pratens (Timothy grass)

P. pratense is a (yet another!) invasive perennial grass which can grow up to 1.5 m tall and spreads vigorously. It is an important forage grass, native to Europe and Asia, which can alter native plant communities by forming monocultures (vegetation consisting of the same species). Its seed is considered a contaminant of grass and other seed lots in the eastern US states of Delaware, Maryland, New Hampshire, New Jersey, Pennsylvania, Virginia and West Virginia, thus reducing seed lot quality and price. P. pratense is also a host to diseases, such as ergot (Claviceps purpurea), that are serious pathogens of cereal crops.

By Walter Siegmund (Own work) [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons

5. Rubus parviflorus

Rubus parviflorus (thimbleberry)

R. parviflorus is a deciduous, perennial raspberry species which produces edible fruits and can act as a soil stabiliser. Its fruits are eaten by the indigenous peoples of North America who also use parts of the plant to treat a wide variety of ailments such as stomach ache and diarrhoea. It is native to North America and Canada, however it has been recorded as invasive in British Columbia, Canada, due to the fact it can outcompete seedlings of economically important conifer species. It has also been recorded as invasive in parts of Europe.

  1. Agropyron cristatum by Franz Xaver (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0) or GFDL (http://www.gnu.org/copyleft/fdl.html)%5D, via Wikimedia Commons
  2. Andropogon glomeratus by Homer Edward Price (Bushy-Bluestem  Uploaded by Amada44) [CC BY 2.0 (http://creativecommons.org/licenses/by/2.0)%5D, via Wikimedia Commons
  3. Atriplex semibaccata by scott.zona (Flickr: Atriplex semibaccata) [CC BY 2.0 (http://creativecommons.org/licenses/by/2.0)%5D, via Wikimedia Commons
  4. Phleum pratense by I, Hugo.arg [GFDL (http://www.gnu.org/copyleft/fdl.html), CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/) or CC BY-SA 2.5-2.0-1.0 (http://creativecommons.org/licenses/by-sa/2.5-2.0-1.0)%5D, via Wikimedia Commons
  5. Rubus parviflorus by Walter Siegmund (Own work) [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)%5D, via Wikimedia Commons

New in November and December 2015 from the ISC

In November and December 2015 the following datasheets were published on CABI’s Invasive Species Compendium (ISC). You can explore the open-access ISC here: www.cabi.org/isc.

By peganum from Henfield, England (Cotoneaster horizontalis) [CC BY-SA 2.0 (http://creativecommons.org/licenses/by-sa/2.0)], via Wikimedia Commons

1. Cotoneaster horizontalis

Cotoneaster horizontalis (wall-spray)

C. horizontalis is a woody, perennial, deciduous or semi-evergreen shrub with horizontally spreading branches, native to parts of China. It is an attractive garden plant with bright red berries which is the main cause for its widespread introduction across the world. In addition to keen gardeners, seeds of this plant are spread easily by birds. Unfortunately, it invades chalk grasslands (such as those of the South Downs in the UK), reducing species richness and diversity.

By Liné1 (Picture taken with my IXUS 800 IS) [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons

2. Cyperus papyrus

Cyperus papyrus (papyrus)

C. papyrus is a tall (up to 5 m), fast-growing, aquatic perennial sedge native to North Africa, well-known as being a source material for the making of paper (papyrus). Plumes of thread-like stems at the top of the plant make it particularly attractive and have resulted in its use as an ornamental plant and consequently its introduction to other countries. It can anchor itself in water via shallow roots or floats freely in clumps, facilitating its spread. The dense and extensive stands it can form can impede the flow of waterways and displace native species. It can reduce the amount of light that reaches submerged plants and can impact on habitats of wetland bird species.

Myroxylon balsamum (Peru balsam)

M. balsamum is a large tree of tropical America (40-45 m tall and 1 m wide) which produces lots of small whitish flowers and winged seedpods. Providing valuable timber and balsam resin, it has been widely introduced. It can form dense stands and can therefore outcompete native species by shading them. Characteristics which make it such a strong competitor include its large size, capacity for prolific seed production and ability to tolerate a wide range of light conditions. It is particularly problematic in Sri Lanka where native species can tolerate less varied light conditions and where natural enemies, such as diseases and insects, are absent.

By Meneerke bloem (Own work) [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons

3. Persicaria wallichii

Persicaria wallichii (Himalayan knotweed)

P. wallichii is a shrubby perennial herb that originates from the temperate western regions of Asia and the Indian subcontinent. It is reported as invasive in its native range of India and its non-native range of Belgium and the UK. In the USA, it can promote the erosion of river banks where it pushes out native stabilizing species, colonizes large areas, but then dies back in the winter. Furthermore, the dense mats of leaf litter it produces can prevent the germination of native species. It can compete for resources with trees and reduce shade along rivers and streams by displacing native woody species.

Roystonea oleracea

4. Roystonea oleracea

Roystonea oleracea (Caribbean royal palm)

R. oleracea is a palm that grows up to 40 m tall, with a distinctive, solitary, light grey, erect, cylindrical trunk. It is native to the Lesser Antilles, northern South America and Guatemala. This invasive species has been widely introduced for ornamental and landscaping purposes. It tends to be invasive in or near wetlands and can reduce diversity in areas where it becomes dominant. The dropping of large leaves and reproductive parts, which alter light intensity and humidity, have been proposed as possible reasons for these impacts. It is reported to be invasive in the swamps of the Guiana shield countries, in Panama and in the Atlantic forests of southern Brazil.

By Frank Vincentz (Own work) [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/)], via Wikimedia Commons

5. Urtica dioica

Urtica dioica (stinging nettle)

U. diocia is a weedy species which, as many people know from experience, has hairs which can cause an itchy sting when touched. It occurs in pastures and grasslands in monospecific clumps which can take up considerable space and thus reduce hay yields and the amount of grass available. It is normally avoided by livestock, therefore restricting their free movement. In some circumstances it can be very hard to eradicate because of its large root mass which allows it to spread vegetatively once it has established.

Other new datasheets published in November and December include:

Acacia glauca (wild dividivi)
Argemone ochroleuca (Mexican poppy)
Canine distemper virus
Centella asiatica (asiatic pennywort)
Deroceras invadens (tramp slug)
Flacourtia indica (governor’s plum)
Portulaca quadrifida (chickenweed)
Solanum capsicoides (cockroach berry)
Tephrosia candida (white tephrosia)
Xyris complanata (yellow-eyed grass)

Figure references:

  1. Cotoneaster horizontalis by peganum from Henfield, England (Cotoneaster horizontalis) [CC BY-SA 2.0 (http://creativecommons.org/licenses/by-sa/2.0)], via Wikimedia Commons
  2. Cyperus papyrus by By Liné1 (Picture taken with my IXUS 800 IS) [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons
  3. Persicaria wallichii by By Meneerke bloem (Own work) [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons
  4. Roystonea oleracea by By Krzysztof Ziarnek, Kenraiz (Own work) [CC BY-SA 4.0 (http://creativecommons.org/licenses/by-sa/4.0)], via Wikimedia Commons
  5. Urtica dioica by By Meneerke bloem (Own work) [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons

 

New in October 2015 from the ISC

In October 2015 the following datasheets were published on CABI’s Invasive Species Compendium (ISC). You can explore the open-access ISC here: www.cabi.org/isc

Forest & Kim Starr [CC BY 3.0 (http://creativecommons.org/licenses/by/3.0)], via Wikimedia Commons

1. Mysore raspberry

Rubus niveus (Mysore raspberry)

Rubus niveus is an invasive blackberry which is threatening the endemic wildlife of the Galapagos Islands. More specifically, it is a threat to the unusual daisy tree forests (of the Scalesia genus). R. niveus now covers around 30,000 ha of the islands and can grow up to 3 m tall. CABI scientists are searching for potential biocontrol agents from the Asian native range of the blackberry to introduce here. Find about more about this project.

Christian Fischer [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons

2. Common knotweed

Polygonum arenastrum (common knotweed)

This species is considered to be one of the world’s most economically important weeds. It is a host of various pathogens which damage crops such as alfalfa, potato and parsnip. Phytotoxic chemicals are produced by the plant that can inhibit the establishment of black medic (Medicago lupulina) and other plant species. It can also affect rhizome bacteria which are important for legume species such as peas and beans. The weed is very resilient as it possesses a long taproot which helps it survive drought.

Forest & Kim Starr [CC BY 3.0 (http://creativecommons.org/licenses/by/3.0)], via Wikimedia Commons

3. Love-vine

Cassytha filiformis (love-vine)

Invasive in its broad native range (Asia, Africa, America, Oceania), Cassytha filiformis is a parasitic vine that is primarily found in coastal areas. In the Chagos archipelago (Indian Ocean) it is seriously reducing populations of beach cabbage (Scaevola taccada) and increasing the risk of erosion. C. filiformis extracts plant sap from its host and covers it with a dense mat of stems. The sheer weight of its stems can break branches – this is particularly problematic when its host is a crop, such as a citrus tree.

 

Forest & Kim Starr [CC BY 3.0 (http://creativecommons.org/licenses/by/3.0)], via Wikimedia Commons

4. Portia tree

Thespesia populnea (portia tree)

Thespesia populnea is an Old World, tropical, coastal species that is often found in and around mangroves. Its buoyant and hardy seeds can survive even after a year in seawater. It produces dark, red-brown, strong and hard ‘milo’ wood that is highly valued on Pacific islands. However, it can form dense thickets and reproduces profusely. It is listed as an invasive species in the Bahamas, Florida and Puerto Rico.

Hypogeococcus pungens (cactus mealybug)

Hypogeococcus pungens is a mealybug, native to South America, which was used as a biological control agent of invasive cacti in the subfamily Cactoideae in Queensland, Australia, and in South Africa. Since then, it has become an invasive species itself. It is a threat to native cacti in Florida and Hawaii (USA), Barbados and other Caribbean islands. In addition to cacti, its wide range of hosts includes species within the ornamental plant families Portulacaceae, Apocynaceae and Amaranthaceae.

Other new datasheets published in October include:

Baccharis pilularis (coyote brush)
Cuphea carthagenensis (Colombian waxweed)
Cyrtomium falcatum (Japanese holly fern)
Epilobium ciliatum (northern willowherb)
Maliarpha separatella (African white rice borer)

Figure references

  1. Mysore raspberry by Forest & Kim Starr [CC BY 3.0 (http://creativecommons.org/licenses/by/3.0)%5D, via Wikimedia Commons
  2. Common knotweed by Christian Fischer [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)%5D, via Wikimedia Commons
  3. Love-vine by Forest & Kim Starr [CC BY 3.0 (http://creativecommons.org/licenses/by/3.0)%5D, via Wikimedia Commons
  4. Portia tree by Forest & Kim Starr [CC BY 3.0 (http://creativecommons.org/licenses/by/3.0)%5D, via Wikimedia Commons

New in September 2015 from the ISC

In September 2015 the following datasheets were published on CABI’s Invasive Species Compendium (ISC). You can explore the open-access ISC here: www.cabi.org/isc

Common mullein by Fritz Geller-Grimm (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0), CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0), GFDL (http://www.gnu.org/copyleft/fdl.html) or CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons

1. Common mullein

Verbascum thapsus (common mullein)

A biennial herb which has naturalized in most temperate regions of the world. It grows vigorously, threatening native plants in meadows and forest gaps. Eradication is extremely difficult since each individual can produce 100,000-175,000 seeds that can remain viable for more than 100 years.

Fibropapillomatosis of sea turtles by Peter Bennett & Ursula Keuper-Bennett (Original photograph) [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC BY 3.0 (http://creativecommons.org/licenses/by/3.0)], via Wikimedia Commons

2. Fibropapillomatosis

Fibropapillomatosis of sea turtles

A disease which most commonly affects the endangered green turtle. It causes internal and external tumours which can obstruct crucial functions such as swimming and feeding. First reported in the 1930s in Florida, it is now a pandemic.

Grey snake-bark maple by KENPEI (KENPEI's photo) [GFDL (http://www.gnu.org/copyleft/fdl.html), CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/) or CC BY-SA 2.1 jp (http://creativecommons.org/licenses/by-sa/2.1/jp/deed.en)], via Wikimedia Commons Mnemiopsis leidyi (sea walnut) http://www.cabi.org/isc/datasheet/75102

3. Grey snake-bark maple

Acer rufinerve (grey snake-bark maple)

With striped grey-green bark this tree is aptly named. It produces dense thickets and has been reported as an aggressive coloniser in acidic forests in Belgium. It has been introduced around the world as an ornamental plant, like so many other invasive species.

Sea walnut by No machine-readable author provided. Bastique assumed (based on copyright claims). [GFDL (http://www.gnu.org/copyleft/fdl.html), CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/) or CC BY-SA 2.5-2.0-1.0 (http://creativecommons.org/licenses/by-sa/2.5-2.0-1.0)], via Wikimedia Commons

4. Sea walnut

Mnemiopsis leidyi (sea walnut)

Being a comb jelly, this marine species has rows of ‘combs’ (groups of cilia) which it uses for swimming. It is an ‘ecosystem engineer’ which can change water transparency and water nutrient content. It has the impressive ability to regenerate from fragments larger than one-quarter of an individual.

 

Ficus microcarpa (Indian laurel tree)

A high-risk, aggressively invasive, strangling fig which is an agricultural weed and “garden thug” – how much worse could it be!? Reportedly invasive to some places where its specialist pollinator wasp has also been introduced. It starts life as an epiphyte, growing on a tree’s surface, before sending its aerial roots down to the ground. The roots end up forming a lattice around the trunk of the host tree which remains after the host tree dies.

Figure references

  1. Common mullein by Fritz Geller-Grimm (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0), CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0), GFDL (http://www.gnu.org/copyleft/fdl.html) or CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)%5D, via Wikimedia Commons
  2. Fibropapillomatosis of green turtle by Peter Bennett & Ursula Keuper-Bennett (Original photograph) [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC BY 3.0 (http://creativecommons.org/licenses/by/3.0)%5D, via Wikimedia Commons
  3. Grey snake-bark maple by KENPEI (KENPEI’s photo) [GFDL (http://www.gnu.org/copyleft/fdl.html), CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/) or CC BY-SA 2.1 jp (http://creativecommons.org/licenses/by-sa/2.1/jp/deed.en)%5D, via Wikimedia Commons
  4. Sea walnut by ‘No machine-readable author provided’. Bastique assumed (based on copyright claims). [GFDL (http://www.gnu.org/copyleft/fdl.html), CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/) or CC BY-SA 2.5-2.0-1.0 (http://creativecommons.org/licenses/by-sa/2.5-2.0-1.0)%5D, via Wikimedia Commons

New in August 2015 from the ISC

In August 2015 the following datasheets were published on CABI’s Invasive Species Compendium (ISC). You can explore the open-access ISC here: www.cabi.org/isc


August

Bidens frondosa (beggarticks) – native to North America, this herbaceous annual has a range of medicinal, herbal and decorative uses and been introduced throughout Europe as well as New Zealand and parts of Asia. The seeds can easily attach to fur and clothes, helping spread the plant to new areas.

Opuntia elatior (red-flower prickly pear) – the prickly pears are proving a prickly problem, with many Opuntia species invasive outside of their native range. O. elatior is less widespread than some, but has still been introduced to India, Southeast Asia, South Africa and Queensland. Biological control has had some success with this species.

Stictococcus vayssierei (cassava root mealybug) – found in Equatorial Africa, S. vayssieri feeds on the root system of the cassava plant, causing leaf-fall, wilting, tip dieback and occasionally death. Although it has only been reported in Cameroon and the Democratic Republic of Congo, the cassava root mealybug can cause yield losses of up to 100% and could pose a major threat to cassava production in Central Africa.

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