The impacts of invasive weeds in Chitwan National Park, Nepal

Mikania (Mikania micrantha) is a tropical vine which is native to the Americas. Often referred to as the ‘Mile-a-Minute Weed,’ mikania grows rapidly in areas of high rainfall and has become highly invasive in parts of Asia and the Pacific. Under the Convention on Biological Diversity, invasive species are defined as alien species that threaten native ecosystems, habitats or species and in Nepal, mikania and other invasive plants such as chromolaena (Chromolaena odorata) are becoming increasingly problematic within the Chitwan National Park (CNP). There, the plants are having a serious negative impact on native grasses, shrubs and the one-horned rhinoceros, and by implication, deer and tiger populations. They are also affecting the local people who reside in the buffer zones and rely on the park for fodder and other materials.

A rhino amongst chromolaena

A rhino amongst chromolaena


In a specific study on mikania, scientists from the National Trust for Nature Conservation, Nepal with support from CABI and the Zoological Society of London have found a significant negative relationship between high mikania coverage and the population of rhinos. This is because the mikania vine smothers the fodder plants that the rhinos feed on. This could also be influencing their movement to other areas of the park where they feed on resources and crops important to local people. This in turn may exacerbate conflict between the residents of the buffer zones and the wildlife in the area.

Deer and Tigers

The reduction in fodder plants is likely also to cause a mirrored decrease in the number of deer in the park. Deer feed on similar plants to the rhinos and the impact of mikania on native vegetation is therefore likely to affect their feeding behaviour in a comparable manner. As a result a decrease in deer numbers is likely to have a negative impact on tiger populations, with tiger numbers being directly related to the populations of their prey.

Local people

The residents of the buffer zones surrounding the CNP are known to rely on the core area of the park for resources such as fodder, which they use to feed their livestock. These residents recognise that fodder availability within the park has decreased and report that collecting materials now takes three times as long as it has in previous years to gather the same amount of fodder. Reduced fodder has been attributed to flooding of the park and the spread of invasive plant species. In particular, a high proportion of local residents report that mikania has a significant negative impact on the fodder growing in the park.

Sustainable control of mikania weed

CABI piloted using a rust fungus (Puccinia spegazzinii) as a classical biological control agent for mikania weed in India. This highly host specific and damaging pathogen has now been released in Papua New Guinea and Taiwan, where it is having a significant impact on the growth of the weed. The rust has recently been released on a number of other Pacific Islands, and could be considered for release in Nepal.

New in November 2014 from the ISC

In November 2014 the following datasheets were published on CABI’s Invasive Species Compendium (ISC). You can explore the open-access ISC here:

Clerodendrum indicum Invasive Species Compendium datasheet

Clerodendrum indicum Invasive Species Compendium datasheet

Clerodendrum indicum (Turk’s turban) – this small shrub, native to temperate and tropical Asia, has been deliberately introduced principally to the Americas as an ornamental. Having long since escaped from cultivation, it is now established in the neotropics. Rapid growth and the ability to reproduce by seeds, rooted cuttings and suckers have contributed to its spread, although C. indicum does not appear to be as invasive as other species in the Clerodendrum cohort.

Potamopyrgus antipodarum (New Zealand mudsnail) – native to New Zealand, this aquatic snail has been introduced to Europe, North America, Australia and Asia. Females are parthenogenetic, meaning they can reproduce without males. This allows a new population to be founded by a single female – and with an average of 230 offspring per adult per year, P. antipodarum can quickly become very abundant. Its ability to survive desiccation for several days allows this snail to be spread by birds and anglers. It is currently considered invasive in Spain, USA and Australia.

Cosmos caudatus (wild cosmos) – thanks to its prolific seed production wild cosmos can cause chaos in the tropics, where its fast growth and height (up to 2.5 m tall) makes it difficult to control. Thought to be native to southern Mexico, it is now found in Asia, Africa, throughout the Americas, Australia and some Pacific islands. C. caudatus is particularly adept at spreading in disturbed areas, pastures and roadsides.


Other invasive species datasheets recently published include:

Cyclosorus parasiticus (parasitic maiden fern)
Vulpia myuros (annual fescue)
Clerodendrum bungei (rose glorybower)

New in October 2014 from the ISC

In October 2014 the following datasheets were published on CABI’s Invasive Species Compendium (ISC). You can explore the open-access ISC here:

Silybum marianum Invasive Species Compendium datasheet

Silybum marianum Invasive Species Compendium datasheet

Silybum marianum (variegated thistle) – this large, aggressive thistle was already recognised as a serious invasive way back in the 1800s. Native to the Mediterranean and parts of Asia and Russia, S. marianum is now present on every continent except Antarctica. Standing up to two metres tall, and armed with a spiky flowerhead and prickly leaves, the thistle can outcompete native plants, swamp farmland and impede the movement of people and animals. If eaten, S. marinaum can cause potentially fatal nitrate poisoning.

Lumbricus terrestris (lob worm) – after more than 2000 years of human-mediated introductions, the humble earthworm is now found in South Africa, India, Australia, New Zealand, Europe and North America, where it has picked up the exciting name nightcrawler. When introduced to an environment lacking native earthworms, L. terrestris can dramatically alter soil profiles. Thick leaf mats are quickly converted to humus, depriving native invertebrates of a habitat, altering the microbial community and changing the chemistry of the forest floor.

Cestrum nocturnum (night jessamine) – native to Central America, this showy and fragrant but toxic shrub is now widespread throughout the Old and New World tropics, where it forms dense thickets that crowd out native flora. Its small and profuse seed means there is a high risk of further introductions. C. nocturnum is known to be invasive in Hawaii, the Cook Islands, Fiji, French Polynesia, Western Samoa, Tonga, New Caledonia and New Zealand.

Other invasive species datasheets recently published include:

Acacia hockii (white thorn acacia)
Amaranthus dubius (spleen amaranth)
Dipsacus fullonum (common teasel)
Ehrharta erecta (panic veldtgrass)
Erodium botrys (long-beaked stork’s bill)
Erodium cicutarium (common storksbill)
Gaillardia pulchella (Indian blanket)
Glechoma hederacea (ground ivy)
Hypochaeris radicata (cat’s ear)
Juncus planifolius (broadleaf rush)
Lactuca floridana (woodland lettuce)
Lolium perenne (perennial ryegrass)
Lonicera maackii (Amur honeysuckle)
Malva pusilla (round-leaved mallow)
Marrubium vulgare (horehound)
Melilotus albus (honey clover)
Mentha pulegium (pennyroyal)
Nasturtium microphyllum (one-row watercress)
Odontonema callistachyum (purple firespike)
Oryza barthii (African annual wild rice)
Oxalis corniculata (creeping woodsorrel)
Parentucellia viscosa (yellow glandweed)
Paspalidium geminatum (Egyptian paspalidium)
Persicaria punctata (dotted smartweed)
Polycarpon tetraphyllum (fourleaf allseed)
Rosa multiflora (multiflora rose)
Rubus rosifolius (roseleaf raspberry)
Sanchezia parvibracteata (sanchezia)
Silene gallica (common catchfly)
Stenotaphrum secundatum (buffalo grass)
Tibouchina herbacea (cane tibouchina)

Invasive myrtle rust impacts discussed at international forestry congress

CABI has recently published a comprehensive review and update of its ISC datasheet on the globally important pathogen Puccinia psidii, commonly known as myrtle rust or guava rust. This problematic fungus is of worldwide importance and is capable of infecting a wide range of hosts. To date it has over 440 host species; affecting many plants in the Myrtaceae family, including threatened and endangered species (see IUCN Red List of Threatened Species). Severe impacts have been recorded in amenity plantings, commercial plantations and the native environment.

Once established in a new country myrtle rust can spread quickly and this has been the case in many countries including Jamaica, Hawaii, Australia and New Caledonia. Its successful global and local dispersal through urediniospores and human-aided movement of diseased plants, combined with its massive host range make myrtle rust an effective and devastating invasive. It was first identified as an invasive pathogen in the 1930s when it caused extensive damage to allspice (Pimenta dioica) plantations in Jamaica.

Puccinia psidii on Melaleuca quinquenervia in Australia

Effects of the invasive myrtle rust (Puccinia psidii) on the paperbark tree (Melaleuca quinquenervia) in Australia (July, 2011)

Discussions of myrtle rust impacts and a variety of other forestry related issues are currently underway at the 24th IUFRO World Congress, which is being held from the 5th-11th October 2014 in Salt Lake City, USA.

IUFRO is the International Union of Forest Research Organizations – the world’s forest network. The organisation promotes global cooperation on forest-related research and is composed of over 15,000 scientists from 650 member organizations in more than 100 countries.

The Congress is the largest forest research conference worldwide and is held every 5 years. It brings together delegates from varying forestry backgrounds and this year over 3500 scientists, researchers, graduates, decision makers, policy makers and land managers are expected to attend the event, which is focused on “Sustaining Forests, Sustaining People: the Role of Research”. Over the course of the week a number of plenary, sub-plenary, technical and poster sessions will cover themes, such as:

Under the theme of Forest Health in a Changing World, a session dedicated to emerging invasive forest pathogens will see notable speakers discuss the impacts of myrtle rust in the southern hemisphere, including its effects on diversity in both Australia and Hawaii (see p103-104 of the Scientific Program). This session will also focus on ash dieback and the invasive pathogen Hymenoscyphus pseudoalbidus, which causes the disease in ash trees. This pathogen has recently been causing severe impacts across Europe.

For full details of the distributions, impacts, descriptions (and much more!) of both ash dieback and myrtle rust you can access the fully updated and peer reviewed datasheets on CABI’s open access Invasive Species Compendium.

To keep up to date with all the latest news from the 24th IUFRO World Congress, visit the blog here.

New in August 2014 from the ISC

In August 2014 the following datasheets were published on CABI’s Invasive Species Compendium (ISC). You can explore the open-access ISC here:

Lepus europaeus (European hare) – the European hare has been widely introduced by humans from its original range in continental Europe and has successfully established populations in South Sweden, North and South America, Australia, New Zealand, Ireland and several Mediterranean and tropical islands. In its introduced range it can cause significant agricultural damage and compete or hybridise with native fauna. Conversely, populations have declined across much of its native range.

Lepus europaeus Invasive Species Compendium datasheet

Lepus europaeus Invasive Species Compendium datasheet

Myxobolus cerebralis (whirling disease agent) – this member of the parasitic myxozoan group causes whirling disease of salmon and trout, which causes fish to swim erratically, making feeding and avoiding predators difficult. M. cerebralis was first reported in Germany in the late 1890s, but, acting in cahoots with its invertebrate host, the sludge worm Tubifex tubifex, it has since spread throughout Europe. The international fish trade has helped it reach Africa, Lebanon, New Zealand and North America, where it may pose a risk to native fish species.

Ardisia crenata (coral berry) – native to east and southeast Asia, this evergreen shrub has introduced around the world and is widely cultivated as an ornamental plant. It invades forest margins and understory, where it can reduce light levels by 70%, thereby shading out native plants.


Other invasive species datasheets recently published include:

Alysicarpus vaginalis (alyce clover)

Caesalpinia pulcherrima (peacock flower)

Cortaderia jubata (purple pampas grass)

Juncus planifolius (broadleaf rush)

Lolium perenne (perennial ryegrass)

Melilotus albus (honey clover)

Mentha pulegium (pennyroyal)

Nasturtium microphyllum (one-row watercress)

Persicaria punctata (dotted smartweed)

Workshop held on future of Invasive Species Compendium

Members of the Invasive Species Consortium from the US, Mexico, Caribbean and South Pacific met in Washington DC on 4 August and unanimously agreed to keep the Invasive Species Compendium (ISC) an open access resource for a further five years. The ISC has been resourced by a diverse international consortium of government departments, development aid organizations and private companies. Consortium members agreed that work on the ISC to date was of global importance and utility, and should continue.

Invasive Species Compendium website

The Invasive Species Compendium website

The ISC is a global encyclopaedic resource that combines science-based information to support decision-making in invasive species management. Invasive species, such as non-native weeds, animals and microorganisms, are one of the main causes of biodiversity and economic loss worldwide, impacting livelihoods and human health. Since its launch, use of the ISC has continued to grow, now with over 400,000 users in 234 different countries. Read more of this post

New in July 2014 from the ISC

In July 2014 the following datasheets were published on CABI’s Invasive Species Compendium (ISC). You can explore the open-access ISC here:

Senna multijuga (November shower) is a shrub or tree native to South America that has been introduced to tropical regions around the world. It is tolerant of a variety of soil types and its seeds are easily dispersed by wind and people. Despite its ability to naturalize quickly and its invasiveness in Hawaii, S. multijuga continues to be spread intentionally as an ornamental plant.

Senna multijuga Invasive Species Compendium datasheet

Senna multijuga Invasive Species Compendium datasheet

Abrus precatorius (rosary pea) is a high-climbing, twining or trailing woody vine from the Old World tropics. Although the plant has a wide variety of uses, from medicine, food and sweetener to jewellery, horticulture and even as a weighing unit, the seeds are so toxic that a single seed can kill a human. This vine is known to be invasive to Cuba and many parts of Asia-Pacific, and is naturalized in many tropical regions including Hawaii, parts of the Marquesas and Singapore.

Senna spectabilis (whitebark senna) – epithets range from ‘environmental weed’ to ‘garden thug’ for this resilient and fast-growing tree. Native to tropical America, S. spectabilis is considered invasive in Australia, Uganda, Tanzania, Hawaii, French Polynesia and Cuba. It can spread rapidly to create monocultures and place native flora at risk.

Other invasive species datasheets recently published include:

Senna surattensis (golden senna)

Senna bacillaris (whitebark senna)


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