Tackling Tutsan

Tutsan (Hypericum androsaemum) is invasive to New Zealand and Australia. Native to many countries throughout Europe and western parts of Asia, it is thought to have been introduced as a garden ornamental by acclimatisation societies in the 1800s due to its attractive yellow flower. Today, tutsan is a severe weed in several regions of New Zealand, most significantly affecting the Ruapehu District and Bay of Plenty region in the North Island. Over the last 20 years, tutsan has become an increasing problem in these regions; spreading throughout low fertility pastures and along roadsides. There is concern that tutsan has the potential to pose a significant conservation threat if it continues to spread at its current rate through scrub and native forest fringes.

Flowering tutsan plants growing in New Zealand (photo: Lizzie Rendell, 2011)

Flowering tutsan plants growing in New Zealand (photo: Lizzie Rendell, 2011)

Recent estimates indicate that around 150,000 ha of land in the Ruapehu district is affected by tutsan. Within the district, the annual cost of controlling the weed, and loss of farming profit amount to around $NZ1.2 million (£600,000), and loss of current land values is estimated at $NZ27 million (£13 million). Tutsan is a persistent weed for which there are no registered chemicals. Off-label herbicides are currently used in an attempt to limit its spread, but these are proving ineffective with stands typically reappearing several years later. The weed is unpalatable to stock and the topography of the region’s worst affected areas further limits the control methods possible.

Tutsan growing on sheep pasture in the Ruapheu District of the North Island, NZ; the copper colour arises from a reddening of the leaves as the plant matures (photo: Lizzie Rendell, 2011)

Tutsan growing on sheep pasture in the Ruapheu District of the North Island, NZ; the copper colour arises from a reddening of the leaves as the plant matures (photo: Lizzie Rendell, 2011)

In 2007 the Tutsan Action Group (TAG) was initiated, formed of local farmers, farm consultants, regional council Pest Plant Officers and representatives from the governmental Department of Conservation to tackle the growing problem. As well as carrying out their own work to raise awareness of tutsan throughout the region, TAG approached Landcare Research to ask for help and in 2009 a biological control programme was established through support from the Ministry for Primary Industries Sustainable Farming Fund.

To date the programme has consisted of an international effort between Landcare Research New Zealand, CABI Switzerland and more recently, CABI UK. Surveys have been carried out in both the invasive and native ranges of the plant to assess the extent of current populations and to identify potential biological control agents. In recent European surveys, a leaf beetle (Chrysolina abchasica) and a tortricid moth (Lathronympha strigana) were identified as having the potential to become biocontrol agents for tutsan and are currently being reared for host range testing by Landcare Research, under quarantine conditions in Lincoln, New Zealand.

The tutsan rust fungus, Melampsora hypericorum was also evident in surveys, both in the native range and in New Zealand. This pathogen has been known to provide control for tutsan populations in Victoria, Australia. In the early 1990s a biological control programme was initiated in Victoria since tutsan was affecting 67,000 ha in the Otaway Ranges. This programme was soon abandoned as surveys revealed that the rust fungus had self-introduced and was already controlling tutsan populations in this region; by 1993, surveys discovered only one live tutsan seedling. In recent times, tutsan is considered to be an increasing problem in Victoria, with the level of control provided by the rust fungus is currently unknown. Melampsora hypericorum is thought to be acting as an effective biological control agent in some parts of New Zealand, for example on some populations of the South Island, but remains ineffective in the regions worst affected. Molecular studies were conducted to establish where tutsan was originally introduced into New Zealand from, and revealed that several introductions are likely to have occurred. Plants in New Zealand’s North Island are likely to have been introduced from Wales or Ireland, and plants in the South Island from the UK, France or Spain. Genetic analysis of both plant and fungal material has also revealed that different genotypes of both tutsan and the rust occur in different regions across New Zealand. The range of genetic variation gives rise to a complex plant-fungal relationship which is playing a major role in the susceptibility of tutsan populations to M. hypericorum.

Current work at CABI, is focusing on assessing the virulence of 14 different strains of M. hypericorum collected from Europe and Georgia towards tutsan plants from New Zealand. Studies aim to find a strain that is more virulent towards the most problematic plant populations of tutsan that are not currently controlled by the rust. To date, the virulence of two strains of M. hypericorum have been assessed. A strain from Georgia failed to infect tutsan populations that are considered most problematic from the North Island. A strain collected from Pembrokeshire, Wales has produced a reliable infection on tutsan plants collected from four different New Zealand populations, including two populations which were ranked as having a high severity in 2011 surveys. Assessment of the remaining 12 rust isolates is currently ongoing.

Since little is currently known about M. hypericorum, trials are also being carried out to assess the infection parameters of the rust fungus. Free water availability and temperature are being investigated to determine the range and peak of these parameters for the species.

Tutsan in inoculation trials at CABI, Egham infected with the tutsan rust fungus, Melampsora hypericorum (photo: Lizzie Rendell, 2014)

Tutsan in inoculation trials at CABI, Egham infected with the tutsan rust fungus, Melampsora hypericorum (photo: Lizzie Rendell, 2014)

Lizzie Rendell

 Scientific Support

Tuta absoluta on the rampage in Africa

Watch a new video illustrating the devastating impacts that Tuta absoluta is having on tomato yields, and what this means for farmers who rely on these crops for sustenance and income.

Dr Arne Witt, from CABI commented on the implications of Tuta absoluta infestation across Africa

“Tomatoes are one of the most widely cultivated crops in Africa and are grown in the backyards of almost every homestead across sub-Saharan Africa. This important cash crop and source of vitamins is now threatened by the recent arrival of the tomato leafminer, Tuta absoluta.

This Invasive Alien Species is rapidly moving down the African continent, having already decimated crops in Egypt, Ethiopia, Kenya and northern Tanzania. Growers are at their wits end as to how best they can control this pest and many have abandoned tomato growing altogether. The race is on to prevent its spread further south with various interventions planned to mitigate its impact in areas where it is already present.”

For more information on Tuta absoluta visit the Invasive Species Compendium and the Plantwise Knowledge Bank.

In the eye of the invasive species storm

17th September 2014 – Last weekend I experienced first-hand the impacts that invasive species can have. While carrying out research on an infestation of Opuntia Stricta in Laikipia, I felt something lodge itself in my eye. The following day I visited a specialist, as efforts to wash the thorn out of my eye had been unsuccessful.

They found that one of the very fine thorns, which are found on the fruit of the cactus, had become trapped in my eyelid and was scraping along the cornea. According to the specialist, another two days with the thorn in my eye would have resulted in me developing a corneal ulcer; which could have cost me my sight in that eye.

The thorns of Opuntia Stricta fruit are incredibly fine. So fine that the specialist was only able to detect it using microscopy equipment and dye. As well as being an unpleasant experience, this incident highlights the serious implications for those who live in areas which are infested with Opuntia Stricta, where many people would be unable to afford to seek medical help should they experience the same thing.

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Opuntia Stricta can also have a significant negative impact on livestock. If they get thorns in their eyes, there is no way for the owner to remove them. This could potentially result in loss of sight. Equally, it is not uncommon for goats to feed on the Opuntia fruit where the same thorns damage the goat’s stomach. This has been linked to the death of many animals in areas where this weed is prevalent as well as overgrazing in uninfected areas which is putting strain on pastoral land in these areas (Dodd, 1940).

While invasive species are often perceived as a biodiversity threat, they have a very real impact on the livelihoods and health of those who live in the areas in which they infest.

CABI releases rust fungus to control invasive weed, Himalayan balsam

26 August 2014 – From today, not-for-profit research organization, CABI, will be releasing a rust fungus at locations in Berkshire, Cornwall and Middlesex as part of field trials to control the non-native, invasive weed Himalayan balsam (Impatiens glandulifera) using natural means.

Himalayan balsam has rapidly become one of the UK’s most widespread invasive weeds, colonizing river banks, waste land, damp woodlands, roadways and railways. The Environment Agency estimates that the weed occupies over 13% of river banks in England and Wales. It can reach over three metres in height and competes with native plants, reducing biodiversity. Large scale chemical and manual control is often not feasible and not economically viable.

Himalayan balsam infestation on the river Torridge, Devon, UK

Himalayan balsam infestation on the river Torridge, Devon, UK (Rob Tanner, CABI)

Using existing measures, the Environment Agency estimates it would cost up to £300 million to eradicate Himalayan balsam from the UK.

The release of the rust fungus comes after an eight-year research programme funded primarily by Defra and the Environment Agency, with contributions from Network Rail, the Scottish Government and Westcountry Rivers Trust. During the course of the research, testing in quarantine laboratories has established that the rust fungus causes significant damage to Himalayan balsam and does not impact on native species.

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New in April 2014 from the ISC

In April 2014 the following datasheets were published on CABI’s Invasive Species Compendium (ISC). You can explore the open-access ISC here: www.cabi.org/isc

Thunbergia alata (black eyed Susan) – Australia, Brazil, Central America and many Pacific islands are all threatened by this aggressive herbaceous vine. Once introduced into a suitable climate, often as an ornamental, it quickly establishes and spreads both sexually and vegetatively. T. alata is capable of smothering native vegetation, killing host trees, out-competing understory plants and negatively affecting the germination and establishment of native plants.

Thunbergia alata Invasive Species Compendium datasheet

Thunbergia alata Invasive Species Compendium datasheet

Indigofera hirsuta (hairy indigo) – native to Africa, Asia and Australia, this herbaceous legume has been widely introduced as a crop and forage plant. Its ability to adapt to a wide range of soil types, spread quickly and regenerate – even in burnt-out ground – has led it become invasive in many Pacific islands. It is also considered a weed in China, Brazil and parts of the USA.

Urochloa mutica (para grass) – U. mutica has been widely introduced to tropical and subtropical regions as a fodder grass. This species’ aggressive growth, high productivity and allelopathic abilities have allowed it to become one of the worst weeds in the USA, Mexico, Central America and Australia.

Other invasive species datasheets recently published include:

Allamanda cathartica (yellow allamanda)

Emilia fosbergii (Florida tassel-flower)

Zingiber zerumbet (shampoo ginger)

Nelsonia canescens (blue pussyleaf)

The XIV International Symposium on the Biological Control of Weeds, Kruger National Park, South Africa, March 2014

In March 156 delegates from 24 countries travelled to the Kruger National Park in South Africa to attend the XIV International Symposium on Biological Control of Weeds (ISBCW) which was held at the Nombolo Mdhuli situated in the Skukuza Camp (2 – 7 March 2014). This quadrennial international symposium is a prestigious conference which provides delegates with an opportunity to present novel research on all aspects of biological weed control, to reflect on past experiences and discuss the way forward for the discipline and – this goes without saying – to catch up with old friendships and forge new ones. Three years on from the previous symposium in Hawaii and timed to commemorate “100 years of weed biological control in South Africa” 1, the African continent hosted the meeting for the second time in its history (the first time being the IX ISBCW held in Stellenbosch, South Africa in 1996). However, perhaps partly because of the increasingly severe constraints on funding and failure to gain official approval from respective governments/organizations, which made it impossible for many people to attend, this year’s symposium saw lower delegate numbers than previous ones. Some of the traditional “strongholds” in weed biocontrol, i.e. Australia, USA and Canada were clearly underrepresented, while the high number of European participants reflected the rapidly increasing interest in weed biocontrol in this part of the world. Sadly, apart from the participants from South Africa, only one other African country (Kenya) was represented. Last, but not least, it was an important and positive feature of attendance at this symposium that up-and-coming, younger scientists from all over the world were very well represented and the presence, prominence and enthusiasm of the next generation of weed biocontrol scientists at the XIV ISBCW seems to bode well for the future of the discipline.

Nombolo Mdhuli Conference Centre, Skukuza Rest Camp, Kruger National Park

Nombolo Mdhuli Conference Centre, Skukuza Rest Camp, Kruger National Park. Host venue for the XIV International Symposium on the Biological Control of Weeds (Photo: Marion Seier)

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New in March 2014 from the ISC

In March 2014 the following datasheets were published on CABI’s Invasive Species Compendium (ISC). You can explore the open-access ISC here: www.cabi.org/isc

Bothriochloa pertusa (pitted beard grass) - B. pertusa is a perennial grass native to eastern and southern Asia. It has been widely introduced in the Americas, Australia and the Pacific, either accidentally or probably in some cases deliberately for use as a forage grass. It has established itself in many native habitats where it is able to out-compete many native species due to its ability to establish dense mats and shade out slower establishing species.

Bothriochloa pertusa Invasive Species Compendium datasheet

Bothriochloa pertusa Invasive Species Compendium datasheet

Portunus segnis (blue swimming crab) – P. segnis is a marine nocturnal crab native to the western Indian Ocean. It is now considered established in the Mediterranean but invasive in the east and potentially invasive in the central and western Mediterranean. It is an active predator, tolerant to a wide range of temperatures and salinities and capable of reproducing throughout the year, with long-lived planktonic larval stages. Global warming is also expected to favour this tropical species.

Xanthium spinosum (bathurst burr) – X. spinosum is a highly invasive plant classified as one of the world’s worst weeds. It is now widely distributed throughout many regions of the world, where it is a common agricultural and pasture weed and a declared noxious species in many countries. Originating in South America, it has spread widely, probably via its spiked seeds which attach to animals and clothing or are a contaminant of hay or other products. It produces prolific amounts of seed that germinate easily. X. spinosum can quickly dominate large areas, outcompeting crops, forage plants and native flora. Control is possible but requires significant effort. There is considerable ongoing research into various methods including biological control.

Other invasive species datasheets recently published include:

Anredera cordifolia (Madeira vine)

Anthoxanthum odoratum (sweet vernal grass)

Opuntia monocantha (common prickly pear)

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