Category: research

Nematodes: the natural nemesis to slugs and other garden pests

Posted on by andy.winfield

By Alida Robey

Nematodes pop up from time-to-time on gardening programmes, but usually as something of an afterthought: “Oh, and of course if you don’t want to use pesticides you can always try nematodes.” A certain air of mystique has surrounded nematodes for some years now, but these environmentally friendly pest controllers warrant far more consideration than a mere afterthought!
Nematodes are in fact one of the most successful and adaptable animals on the planet. They are second only to the insects in their diversity of species, geographic spread and the range of habitats they can occupy. There are more than 15,000 known species of nematodes, more commonly known as roundworms, and likely thousands more that are yet to be described.
There are parasitic nematodes that live in the gut of animals, humans, birds and mammals. Other species are free-living in the soil, feeding on bacteria and garden waste. Some are parasitic on plants and may cause disease and crop devastation. But, as a gardener, I’m most interested in those species that are free-living in healthy soil and those that parasitise common garden pests.
Free-living garden nematodes are microscopic thread-like worms, which are scarcely visible without a microscope. (This is in marked contrast to the 9 metre long species, Placentonemagigantissima, which can be found in the placenta of the sperm whale!). In good nutritious soil there could be as many as 3 billion individuals per acre. They eat fungi, bacteria and algae. So, much like ordinary earthworms, they have a useful role in decomposing and recycling nutrients.

Biological control with a specific target

Parasitic species have an equally important role in the garden. With such a diversity of species, it is not surprising to find that there are nematodes that specifically parasitise slugs, ants, vine weevil, leather jacket, chafer grub – you name it! This means that a slug nematode won’t have any impact on anything but slugs – this isn’t always the case with other biological controls and rarely the case with chemical controls.
A wax moth pupa can be a host to thousands of
nematodes. The parasitised cadavers can be placed in
orchards to protect crops from pests such as citrus root and black
vine weevils.
Photo credit: Peggy Greb, US Department of Agriculture
It works like this: the juvenile nematodes are in the soil looking for a specific host. Once found, the nematode enters the body of the host and gives off  bacteria inside the host’s body. These bacteria multiply and cause blood poisoning and, eventually, death. The nematodes then feed on the body of the creature and multiply, sending a new generation off into the soil to find another host. When hosts are scarce, the nematodes naturally die off.

The practicalities of using nematodes

As nematodes are living organisms they have a very limited shelf life. They therefore need to be bought online, stored according to instructions and used very soon after delivery.
There are several UK suppliers of nematodes.
It is important to choose the correct nematode species for the right type of pest and to use them in the right conditions. The soil temperature has to be above 5oC (and remain so) and they should be applied only when the pests or their larvae are active. Nematodes are also light sensitive, so use them early morning or dusk, when light levels are low.
They come as a thick paste in a little sachet, which you need to dilute with water. Repeat applications may be needed.

The specifics:

Ants : Drench the nests between April and September.
Chafer grubs: Apply nematodes in August and early September.
Fruit flies, carrot root fly, onion fly, gooseberry sawfly and codling moth: All of these pests can be treated with a generic nematode mix called Nemasys Natural Fruit and Veg Protection Pest Control. You can use it as a general treatment after planting out and when the soil has warmed up, or to target specific pests when you see them, such as gooseberry sawfly caterpillars. These (and other caterpillars) need to have direct contact with the spray while they are on the leaves.
Leather jackets:  These are the larvae of the crane fly or daddy longlegs and attack the roots of grass in the lawn. Treat with nematodes in the autumn, when the adult daddy-long-legs are laying.
Slugs:  The nematode for slugs was discovered by scientists at the University of Bristol! An application early in spring will tackle the young slugs growing under the ground, which are feeding on humus. A single application should last for at least 6 weeks, which allows time for tender seedlings and young plants to get established. They can be applied until early Autumn.
If using on potatoes, apply them 6-7 weeks before harvesting , when the tubers are most likely to be eaten by slugs.
Slug nematodes are very efficient, enjoying the same wet environment so loved by the slugs themselves.
Vine weevils: An application in March will give much greater control of larvae when they are present – either March to May, or from July to October.
I have heard the anecdotes from many gardeners who have had good results using nematodes for ants, vine weevils and slugs. But in May 2016, the Royal Horticultural Society and BASF, the only UK manufacturer of nematodes, announced a one-year research project to put slug nematodes to the test.
So in May 2017, we should see just how well this little creature stacks up against the chemical and other treatments in tackling arguably our most annoying garden pest.

Alida Robey has a small gardening business in Bristol. For several years in New Zealand she worked with others to support projects to establish composting on both domestic and a ‘city-to-farm’ basis.

Know your knotweed advice

Posted on by andy.winfield

By Nicola Temple

Researchers at the University of Exeter‘s Penryn campus have had a comprehensive look at Japanese knotweed (Fallopia japonica)  guidance from a range of sources on the web, including government sites, environmental NGOs, weed control companies, the media and the property market. They’ve found that this advice is often contradictory and even misleading.

A Japanese knotweed contaminated area in Hertfordshire
is identified with signage.
Photo credit: Peter O’Connor via Flickr [CC By-SA 2.0]
Japanese knotweed was introduced to the UK as an ornamental in the mid-1800s. It quickly became a problem plant, spreading swiftly and widely across the UK. This brutish invasive can penetrate building foundations and drains and is estimated to cost the UK economy £165 million a year.
The plant can grow from very small fragments of rhizome that weigh as little 0.01 g [1]. The rhizome material is capable of surviving for three months in a salty environment, which allows it to spread in coastal regions. Disturbing the rhizomes underground only promote growth and cutting the material above ground stimulates new above ground stems. It is the very definition of nuisance.

Japanese knotweed and the law

Two pieces of legislation were enacted to  provide the legal teeth needed to help control Japanese knotweed [2]. Under the Wildlife and Countryside Act 1981 (Section 14), it is illegal to plant or otherwise cause Japanese knotweed to grow in the wild. Offences can carry a maximum £5,000 fine or six months in prison, or both, in magistrates court. A Crown Court can impose an unlimited fine or maximum prison sentence of 2 years, or both.
The second piece of legislation is under the Environmental Protection Act 1990 (Section 33), where it is classed as ‘controlled waste# and must therefore be disposed of according to the Environmental Protection Act (Duty of Care) Regulations 1991. If you keep, treat or dispose of knotweed in a manner that is likely to allow it to spread, a magistrates court can impose a maximum fine of £20,000 or prison sentence of 6 months, or both. A Crown Court can impose an unlimited fine or maximum prison sentence of 2 years, or both.
Allowing Japanese knotweed to spread to your neighbours can also be considered a private nuisance. Failure to control this plant on your land could therefore result in a prosecution or community protection notice.

Mixed messages

Japanese knotweed growing along a fence in East London.
Photo credit: Gordon Joly via Flickr [CC licence BY-SA 2.0]

The research, published today (4th July) in the journal Applied Ecology, included a content analysis, which objectively describes written, spoken and visual communication, and allows researchers to quantify different types of content. This is a method often used in social research, but rarely applied to ecological questions, such as invasive plants. The results showed that there is conflicting advice out there, particularly about the disposal of Japanese knotweed, which could result in people taking the wrong course of action that leads to the unlawful and environmentally harmful spread of the plant.
“It is important to provide clear advice about the waste disposal of Japanese knotweed,” explained Beth Robinson, a PhD researcher in Exeter’s Environment and Sustainability Institute and lead author of the study, “as it can regrow from small fragments of rhizome and incorrect disposal of waste material can result in further spread of this plant.”
Even government websites were found to have conflicting and unclear information. The researchers point to Devon and Cornwall councils as both having valuable and accurate information about knotweed management. However, most of us are likely to consult the website of our own local council with the assumption that the information they provide is accurate.
“We recommend that local and national authorities collaborate and work towards disseminating more consistent messages,” said Robinson.
A tendency by the media to sensationalise the risks associated with this invasive plant can lead to unnecessary anxiety and expenditure.  An extreme example of this was headlines in 2013 such as ‘Murder andsuicide by husband driven mad over knotweed‘. Stories such as this make it sound as though the plant might have a psychoactive effect – driving people mad by its sheer presence, when indeed there are serious underlying mental health issues.
The Exeter researchers stress that Japanese knotweed needs to be dealt with on a case by case basis. While some knotweed invasions do require professional assistance, small-scale occurrences in domestic gardens may be effectively controlled and disposed of responsibly by the homeowner.

Visit the Cornwall Council website for some reliable information about Japanese knotweed and its management. 


The paper in Applied Ecology is titled ‘Weeds on the web: conflicting management advice about an invasive non-native plant’ and is authored by Beth S. Robinson, Richard Inger, Sarah L. Crowley and Kevin J. Gaston.


Sources:

[1]     Macfarlane, J.S. (2011) Development of Strategies for the Control and Eradication of Japanese Knotweed [MPhil Thesis, University of Exeter] <https://ore.exeter.ac.uk/repository/handle/10871/11862>

[2]     Cornwall County Council (2016) ‘Japanese Knotweed Legal Issues’ [website accessed 4/7/2016] <https://www.cornwall.gov.uk/environment-and-planning/trees-hedges-and-woodland/invasive-plants/japanese-knotweed/japanese-knotweed-legal-issues/>

Bristol is buzzing, how the city is helping pollinators

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By Helen Roberts

There has been a substantial amount of press coverage recently on the plight of our pollinators. They are now less abundant and widespread than they were in the 1950s. A number of threats are responsible, including habitat loss, disease, extreme weather, climate change and pesticide use.
A swathe of flowers for pollinators bring a
lot of cheeriness on a grey autumn day on
Horfield Common, Bristol.
Photo credit: Nicola Temple
There is not one smoking gun among these threats, but rather the combination that has endangered some species in the UK. Loss of wild flower rich habitat (due to intensive agriculture, industrialisation and urbanisation) escalates the effect of disease, extreme weather, climate change and pesticide use. Without food or shelter, pollinators are more vulnerable.

 Whilst visiting the University of Bristol Botanic Garden this autumn, I noticed the abundance of pollinators busily visiting many different flowers from the orchid look-a-like flower of Impatiens tinctoria to the swathes of Rudbeckia sp. and Verbena bonariensis. This year saw the 6th year of the University of Bristol Botanic Garden hosting the Bee and Pollination Festival in September. The Community Ecology Group from Bristol’s School of Biological Sciences was exhibiting and promoting their research as well as the exciting Get Bristol Buzzing initiative.
To find out more about pollinator research at the University, I met up with Dr Katherine Baldock, a Natural Environment Research Council Knowledge Exchange Fellow from the School of Biological Sciences and the Cabot Institute, to discuss the group’s work.
“Most people know that pollinators are important, but quite often don’t know what to do to help them, “ explained Katherine. “And this is where our research at the University comes into play”.
The aim of Katherine’s fellowship is to improve the value of the UK’s urban areas for pollinators by working with various stakeholders, such as city councils, conservation practitioners and the landscape industry. 

Translating science into solutions

NERC KE Fellow Dr Katherine Baldock.
Photo credit: Nicola Temple.

Up until 2014, Katherine worked on the Urban PollinatorsProject, which is researching insect pollinators and the plants they forage on in urban habitats.
Building upon research from this project and her current Fellowship, Katherine and her Bristol colleagues have contributed to the development of  a Greater Bristol Pollinator Strategy(2015-2020). The University research group has teamed up with Bristol CityCouncil, the Avon Wildlife Trust, Friends of the Earth Bristol, Buglife, SouthGloucestershire Council and the University of the West of England to implement this with the aim of protecting existing habitat and increasing pollinator habitat in the Greater Bristol area.
The group is also raising awareness of the importance of pollinators to a wide-ranging audience within the city and further afield. This is the first local pollinator strategy within the UK and follows closely in the wake of the Department for Environment, Food and Rural Affairs’ National Pollinator Strategy launched in 2014. It will help to promote aspects of the national strategy relevant to urban areas and hopefully set a precedent for the development of other local pollinator strategies throughout the UK.
The local pollinator strategy outlines actions that will help fulfill the strategy aims, including:
·         formation of a Local Pollinator Forum intended to share knowledge and best practice,
·         establishment of a joined-up approach to pollinator conservation by linking projects through the Get Bristol Buzzing initiative,
·         working with the public in local areas to explain actions they can take as individuals.
“Urban green spaces are important corridors for wildlife and help to provide linkages across the country”, explained Katherine. I envisaged a series of insect aerial motorways linking the whole of the UK, invisible threads connecting countryside, urban fringe and city centres.

The bee link-up

The Get Bristol Buzzing initiative is doing just that, as one of its strategic aims with the local pollinator strategy for 2016-2020, is to “Map pollinator habitat and identify target sites that allow habitat networks and stepping stones to be created to enable pollinators to move through urban areas”.
Katherine talked about how engaging the public at ground level was really important to Get Bristol Buzzing. The initiative is the pollinator component of My Wild City, a project whose vision is for people in Bristol to help transform spaces into a city-wide nature reserve. A number of interactive maps have been created that allow people to add what they have been doing in their area to help wildlife. The Get Buzzing initiative will feed into these maps.
Kath said, “The fact that you can add yourselves onto a map makes the Get Buzzing Initiative really visually appealing to people and much more personal.”

So, what can you do at home to help urban pollinators?

·         Plant for pollinators. Think about what plants you have in your garden. Could you change the planting or improve on it to make it more attractive to pollinators? Think about growing species that have nectar and pollen rich flowers and let your lawn grow longer to allow plants to flower.
·         Avoid pesticides. Most gardeners like their plants to remain pest free but avoid the temptation to use pesticides and accept the fact that you will lose some plants to pests. Instead try to encourage wildlife that will devour those pests or cultivate plants that will deter pests. 
·         Provide habitat. As pollinators need a home, you can always make your own nest boxes if you want to give your pollinating visitors a helping hand by drilling holes in a log or by bundling up lengths of hollow sticks such as bamboo. Visit the Botanic Garden’s bee hotel for inspiration!
“Setting aside a wild bit of garden can help pollinators by providing food, but provides nesting sites too”, remarked Katherine.

Additional information:

·         The Urban Pollinators Project was recently listed as one of the top 10 ground-breaking research projects in the Daily Telegraph. Read more.

·         Results from this research have recently been published in the Proceedings of the Royal Society B with more publications in press. A list of publications can be found here.

·         You can read more about Dr Katherine Baldock and the Urban Pollinators Project on page 7 of the 2015 edition of the Cabot Institute’s magazine.

Botanists disperse some ‘big data’

Posted on by andy.winfield
Recently, Botanists at Trinity College Dublin launched a database with information that documents significant ‘life events’ for nearly 600 plant species across the globe. The database is the result of contributions from individuals working across five different continents, who compiled information on plant life histories for a near 50-year span, and is an example of big data.

What is ‘big data’?

Black pine (Pinus nigra), one of the species whose life
history data is part of the database, is seen against a
stunning backdrop of New Zealand. Credit: Yvonne Buckley.

In academic circles, the buzz-term across all disciplines seems to be ‘big data’, and it means exactly what it sounds like – a whole lot of information. More formally, of course, big data refers to data sets that are so large and complex that traditional methods of processing the information contained within them simply aren’t adequate. Big data draw upon many sources of information and represent a body of work that far exceeds what a single researcher, or indeed an entire research group, could gather in their careers.
While there are many challenges of working with big data – storing it, analysing, visualising it and ensuring its integrity to name a few – the benefits of working with such large data sets may make overcoming these challenges worthwhile. Repositories of such vast amounts of information can not only help foster collaborations, but they can be used to answer questions surrounding some of the most complex and pressing issues society currently faces, including climate change, food security, and mass species extinctions.
Of course, what is considered to be big data today will not be big data tomorrow as our management systems and computing capacity improve. This is the inevitable path of technological advancement; the Human Genome Project took over ten years (1990-2003) to sequence the human genome and now it can be done in a day for a fraction of the cost.

The importance of sharing knowledge

Plantago lanceolata at Howth Head, Dublin, Ireland – one of
the near 600 plant species that researchers have gathered
extensive life history data on. Credit: Anna Csergo.

The researchers at Trinity have made their database, called COMPADRE, freely available in the hope that other scientists access the information to advance their research. The size of the database means it can be used to help answer an infinite number of questions – such as how plant communities may respond to climate change or physiological processes that might provide insights into our own aging and health.
“Making the database freely available is our 21stCentury revamp of the similarly inspired investments in living plant collections that were made to botanic gardens through the centuries;” said Yvonne Buckley, Professor of Zoology at Trinity’s School of Natural Sciences, “these were also set up to bring economic, medicinal and agricultural advantages of plants to people all over the world. Our database is moving this gift into the digital age of ‘Big Data’.”
The approach of free knowledge sharing is becoming more common and is a critical step toward resolving some of our biggest challenges. The University of Bristol’s Cereal Genomics Group has made the wheat genome along with hundreds of thousands of molecular markers freely available through their searchable database CerealsDB. These data can be used in wheat breeding programmes to develop new varieties of wheat that are more resistant to disease or droughts or produce higher yields.

Our best chance of overcoming some of the global challenges of the 21st Century is to work together. Sharing knowledge through databases, such as COMPADRE and CerealsDB, will ensure every scientific contribution counts towards this united effort.

Beans and bacteria – a complex story of communication

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The symbiotic relationship between legumes and soil bacteria has been known for well over a century. The intimate details of this relationship, however, are only recently being revealed. It is a very active area of research as understanding this symbiotic relationship could lead to strategies that help reduce the environmental impacts of food production. 
Rhizobia nodules on the roots of cowpea
(Vigna unguiculata). By Stdout
[GFDL (http://www.gnu.org/copyleft/fdl.html),
via Wikimedia Commons.
Special soil bacteria – known as rhizobia – reside within the nodules of legumes, such as peas, lentils, beans, alfalfa and clover, which are found along the roots of these plants. The bacteria take nitrogen from the air and convert it into ammonia, which the plant is able to use – a process known as nitrogen “fixing”.
This allows legumes to grow well in nitrogen-poor soils. This nitrogen is taken up in the plant material, which can then be worked back into the soil as a natural fertiliser for subsequent crops.
While this all might sound very straight forward – there are details about this relationship that remain unclear. How do the bacteria get into the nodules? Are there signals that the plant uses to stimulate the bacteria to produce nitrogen?

An answer to a century-old debate

In 2011, researchers from the John Innes Centre in Norwich answered the mystery of how nitrogen-fixing bacteria crossed the cell walls into the nodules of legumes. 
It had been a century-old debate as to whether bacteria produced the enzymes to break down the cell walls or whether the plant did. The researchers showed that it was the plant which supplied the enzymes to break down its cell walls in order to give the bacteria access.

How legumes communicate with their symbiotic bacteria

In 2010, Stanfordresearchers discovered the gene in plants that triggered the chemical signal required for the bacteria to fix nitrogen. They found that the rhizobia bacteria would just sit around in the legume nodules if the plant failed to produce the protein that’s required to spur the bacteria into nitrogen fixing mode. This was only part of the communication story.
It is energetically costly for the plant to produce and maintain the root nodules in which the bacteria live; usually the benefit of having a supply of nitrogen outweighs this cost. If there is sufficient useable nitrogen in the soil, however, the plant is able to reduce the number of nodules on its roots.
Communication between the shoots of the plant and the roots of the plant help regulate the number of nodules. The leaves transmit a signal to the roots to either develop more or get rid of rood nodules, depending on circumstances. The roots communicate back up to the leaves using molecules known as peptides.
Research published recently has now discovered that the plant shoots use plant hormones, known as cytokinins, which travel down the phloem into the roots to help regulate nodule development.

The environmental benefits of understanding legumes

Understanding the symbiotic relationship between legumes and soil bacteria is not simply a matter of scientific curiosity. The ability for legumes to produce natural nitrogen fertilisers is a trait that US researchers would like to potentially transfer to non-legume crops as a way of reducing the environmental impact of agriculture.
Manufacturing nitrogen fertilisers for non-legumes is extremely resource intensive. It has been estimated that to produce 68 kg (150 lbs) of nitrogen fertiliser – enough for one acre of corn – would be the equivalent of driving a car 1,046 km (650 miles).
Beyond that, nitrogen fertilisers release the powerful greenhouse gas, nitrous oxide, after they’ve been applied. Excess fertilisers also runoff agricultural land into rivers and lakes and eventually out into the ocean. This influx of nitrogen can provoke algal blooms and create oxygen deplete dead zones.

Therefore, there is great incentive to fully understand this relationship legumes have with soil bacteria. The environmental impact of agriculture could be significantly reduced by utilising legumes with their natural nitrogen fertiliser more by using them in more marginal land and using traditional breeding programs to select for drought resistance or temperature tolerance. In some countries, genetic engineering might even be used to introduce nitrogen-fixing abilities into non-legume species. Genetic modification, however, can be an inflammatory issue with considerable debate as to its pros and cons, particularly with respect to its use in food products.

‘Tis the season of seed cleaning

Posted on by andy.winfield
Weeks ago, Nick suggested I come in on a rainy day to the garden as there was lots of seed cleaning going on in the potting shed. Then it didn’t rain for three weeks. Defeated by the glorious Autumn weather we’ve had, I phoned Froggie, and asked whether I could come in to learn about seed washing…yes, that’s right, I said “washing”. I’m such an amateur! However, Froggie was kind and  refrained from laughing at me and just said, “we don’t really wash the seeds unless they have a particularly fleshy covering”.
We arranged a time for me to come in and, as it happened, it was yet another glorious sunny day. While this made for a nice bicycle commute for me, it meant that the volunteer gardeners were all out in the garden so I would be having an individual, hands-on learning experience with respect to seed cleaning.

So many envelopes

As Froggie and I entered the potting shed, she took me immediately over to a bench lined with trays in which rows of envelopes were stacked up. On the outside of each envelope is written the plant’s latin name, the family name, the year the seed was collected, which collection the plant is from, the accession number and a number that corresponds with its numbered listing in the Garden’s Index Seminum. This is a catalogue of the seeds and spores that have been collected in association with the University of Bristol Botanic Garden. This catalogue goes out annually to the Friends of the Garden, other Botanic Gardens and research institutes. Requests can be made for small quantities of seed for the purposes of research, breeding, conservation and education, or by members of the Friends of the Garden (subject to certain conditions).
The Garden likes to keep three years worth of seeds, but obviously different seeds have different storage potential. Some species, such as those in the Apiaceae family, which includes celery and parsnips, are generally only viable for a year, while other seeds have been found in archaeological digs that are estimated to be thousands of years old and have remained viable (see the 2,000 year old Judean date palm as an example).
Separating the seeds of Salvia forsskaolii. 
“We’ll keep back older years from groups such as the cereals, oats and wheat, as well as beans and peas,” said Froggie, “as they will likely remain viable and it’s good to have a reserve.”
Froggie explains that with the Garden’s involvement in the Seeds of Change project, there are even more demands on their seed stores. Though schools and community groups are encouraged to collect their own seed, the Botanic Garden is sending out lots of seed to start the projects off or replenish projects where collection efforts haven’t been successful.
In the little office at the back of the potting shed there are even more trays of seeds. This is where the staff compile all the seeds that go on the Botanic Garden’s annual seed list. Now having a sense of what the end product looks like, I sense that Froggie is about to show me how much work goes into filling each of these envelopes…

Separating the seed from the chaff

Pouring the Salvia seeds into a sieve to get
rid of the chaff.
I’m shown yet more trays of envelopes – but much bigger envelopes this time – many with stems poking out the top. The gardening staff and volunteers have collected the seed heads and placed them in these envelopes ready for cleaning and this is where the work begins. Froggie picks out the first envelope, it’s Salvia forsskaolii, commonly known as Indigo woodland sage.
We sit at the table, each with a white tray nestled within a larger black tray, which I assume is to collect the seeds that catapult out beyond the borders of my white tray. Froggie doles out a few sprigs of dried plant and shows me that the best technique for this particular plant is a simple flick of the seed head to help release the seeds. I flick and my white tray is scattered in small black seeds. Easy.
With the larger unwanted bits removed, we now pour our tray contents into a sieve to clean the seeds of any smaller bits. The clean seed is then poured into a smaller envelope that is placed back into the big envelope with the remaining plant material that is yet to be cleaned. When all the plant material has been worked, Froggie will then process the seed envelope, doing and final quality control check on the seed and making sure all the information is clearly written on the envelope.  
Nigella damascena before we begin to collect the seed.
We wipe down our trays and spray an anti-static spray to ensure there is no contamination as we move on to our next species – Nigella damascena. This too requires a tapping method, though some persistent seeds need to be squeezed out. There are numerous implements on the table for crushing plant material to get at the seed, but Froggies says they try to discourage crushing as much as possible as it makes for a lot of fine chaff that is difficult to separate out later.
As we work, Froggie fields questions from the volunteer gardeners who are looking for equipment or just confirming that what they’re doing is right. As we work, Froggie relays a few stories about misguided efforts of volunteers – stories of pruning gone awry or cutting back incorrect species – she chuckles about it all and has an ‘it all grows back’ sort of attitude about it. I know Froggie no doubt has a million other things she needs to be doing, but she gives me her full attention and focus and makes me feel as though she has all the time in the world for me. She creates a calming atmosphere, which no doubt comes in very handy when coordinating the efforts of so many volunteer gardeners and teaching new skills.
What my tray looks like after I’ve removed the Nigella seeds
from the seed heads. 
There is quite a bit of fine material mixed in with the Nigella seeds and so Froggie introduces me to another technique for separating seed from chaff. She takes some newspaper and folds it in half and pours seed and fine chaff together onto the paper. Then with a motion not dissimilar from a chef tossing almonds in a skillet, she carefully tosses the seeds in the paper. The fine, lightweight chaff moves to the top of the crease in the paper, while the heavier seeds move down. She can then simply give a very gentle blow to get rid of the chaff off the top of the paper. In the end she’s left with just the clean seeds.
We start on the last one – Avena orientalis – a grass. For this seed you hold the spikelet in one hand and flick the seed out. This particular species has a lovely dark seed, so it is very clear when you’ve got it all separated. 
Froggie uses newspaper to separate the lightweight chaff
from the heavier Nigella seeds.
Not all the seed cleaning is this easy. There are dust masks as some can be particularly dusty – but the staff tend to do the really nasty seed cleaning themselves, letting volunteers do the easier ones. If this were a rainy day, there would be volunteers everywhere working on this and having a good old chat.
Looking at the stacks of envelopes, I ask Froggie when seed cleaning needs to be finished.
“We need it all complete by February at the latest,” Froggie replies. “The seed list goes out in February and people will start to put requests in. We also start sowing at the end of February, beginning of March.”

Checking the lists

Cleaned Avena orientalis seeds with the
lighter leftover spikelets in the background.

In many of my excursions to the garden, the staff have introduced me to the many lists that they keep. There is a seed sowing list, a putting the garden to bed list, and now, I have seen the seed collecting list. This is where the staff make notes against each species – for example, if a plant was too small or late to come into flower. These notes are kept year to year and so if a species is less productive in one area of the garden than another or from one year to the next, all of this information is captured.
“The list is never finished,” says Froggie. “I will just update it when something else changes.”
In years where they are unable to collect seed for a particular species, they draw upon their reserves from previous year so that it can remain on the seed list. Annuals tend to be a priority, but also shrubs. The Garden works hard to insure that there is variety on the seed list.
As a member of the Friends of the Garden myself, I now look forward to receiving the seed list next year and I will have a much better appreciation of the work that goes into collecting the seeds for each of the nearly 200 species listed.

Forests may be more vulnerable to pests and disease in the future

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As I sit in my home office watching the autumn rains and winds strip the last remaining colourful leaves off the trees outside, I find myself in awe of the tree. There’s a primary school across the street from my house and there are several huge beautiful chestnuts in its grounds where I watched the children shelter from the sun on hot days. There’s also the spindliest little apple tree that one could imagine, which despite its size produced at least a dozen enormous apples this year!
Trees affect every aspect of our lives – they provide food, timber, pulp and fibre, but beyond this they have important ecosystem functions in the natural landscape. Trees help to regulate our climate, they store and sequester carbon (about 30% of global CO2 emissions are absorbed by forests), they store water helping to prevent floods, they purify water and they provide habitat.
However, widespread pests and diseases have taken their toll on natural forests over the past century with outbreaks seemingly becoming more frequent and widespread in recent years. There has been considerable focus on the devastating effects of these outbreaks on trees with large economic value – orchards and timber plantations for example – but what are the consequences of the widespread death of our forests in terms of ecosystem services?
Oak in its autumn colours.
A review published recently in the journal Science considers this exact issue. UK researchers from the Universities of St. Andrews, Cambridge and Oxford reviewed the consequences of tree pests and diseases on ecosystem services around the globe.  The authors concluded that our current approaches to pest and disease management do not take into account the ecosystem services or the beneficiaries of these services provided by forests and that new approaches are needed, particularly as the likelihood of pest and disease outbreaks increases as a result of global climate change and globalisation.

Who’s attacking our forests?

Trees are attacked by any number of pests and diseases, including bacteria, viruses, invertebrates, water molds and fungi. The effects of these pathogens may be compounded as well; trees that have been defoliated by insects may be more vulnerable to disease.
Millions of years of co-evolution have generally allowed trees to build up natural defenses to the pathogens they encounter in their native environments.  However, the introduction of species or the movement of species outside their historical ranges has opened up a whole new world of pathogens that have been the cause of the most devastating attacks on our global forests in the last 200 years.
The American chestnut (Castanea dentata) was devastated by chestnut blight – a fungus accidentally introduced to eastern North American forests around 1900. In the early 20thcentury, over a quarter of the trees across approximately 200 million acres of eastern hardwood forests were American chestnuts, but by 1993 its frequency had declined to 0.5%. Today the tree is effectively extinct as very few mature trees are producing nuts.
Dutch elm disease – another fungal pathogen, which is transmitted by bark beetles – is familiar both in North America and Europe as it has eliminated mature elms (Ulmus spp.) from much of the landscape. Now there is concern that ash (Fraxinus excelsior) could suffer the same fate due to another fungal pathogen (Chalara fraxinea), which has been killing trees in Poland since the 1990s. Scientists are monitoring its spread to the rest of Europe.
The devastation wreaked on a Canadian forest by the
mountain pine beetle. Credit: D. Huber, Simon Fraser University
Public Affairs and Media Relations (Flickr CC).
As a Canadian I would be remiss if I didn’t also mention the devastating effects of the mountain pine beetle (Dendroctonus ponderosae). It has already killed several million hectares of pine species in Canada and the US and they expect over 37 million hectares of forest to be affected in British Columbia alone before 2020.
Of course, with globalisation and the widespread movement of plants and plant products around the world, the frequency and spread of pests and disease is only likely to increase. Climate change will also improve conditions for pests and disease as milder conditions in some areas may let some pathogens increase their natural range, or may permit pest populations to explode in numbers.

Attack of the Frankenfungus


When pathogens move around the globe they are not only introduced to new hosts and plant prey, they can also escape the natural predators and diseases that keep their populations under control.
This global movement also exposes pathogens to new genes that can make them even more virulent. For example, when the fungus that causes Dutch elm disease, Ophiostoma novo-ulmi, spread across the northern hemisphere, it hybridised with a native fungus species (O. ulmi) and acquired some new genes that decreased the elm’s ability to resist infection.   

What does the loss of dominant tree species mean for our forests?

Widespread loss of a dominant tree species can have devastating effects far beyond any economic value they may have had. A wide range of ecosystem services will initially be harmed, such as retention and purification of water, wildlife habitat and carbon storage. Large stands of dead trees also become fuel for wildfires, which are far less specific about their victims and further alter the ecosystem.
However, inevitably the lost trees are replaced by new species and as this natural succession occurs some of the ecosystem services will be restored – carbon storage and water purification, for example. Unfortunately, other ecosystem services may never be restored. New tree species will create different habitats altering the biodiversity. 
Some ecosystems are particularly vulnerable as they are dominated by a species that plays a critical role in maintaining the structure of that ecological community – known as a keystone species. Boreal forest (or taiga) is an excellent example of this. The conifers that dominate the northern latitudes of boreal regions are adapted to short growing seasons, recurring disturbance from storms, fire and floods, and growing in peatlands. Loss of any species in these regions would have a significant impact on the ecosystem structure.

Climate change packs a one-two punch for forests

Not only does climate change have the potential to increase the numbers and range of pests and disease, it can also make forests more susceptible to these infestations. Though the future is uncertain, predicted increases in extreme weather events – droughts, floods, cyclones, and extreme temperature fluctuations – are likely to put our forests under severe stress, increasing their vulnerability. 
Of course, some pests may also be hindered by climate change. For instance, species that rely on an insulating blanket of snow to overwinter may be more vulnerable if snow cover is reduced in a milder climate scenario.

What is the future of our forests?

Nobody knows the answer to this question. However, the UK authors of the Science paper bring to light the need to do more fundamental research in understanding how pathogens affect natural forest communities. To date, most research has focussed on economically important species, yet the ecological role of forests and the ecosystem services they provide have considerable value also.
The long life span of trees has been a barrier to understanding some aspects of the infection and spread of some pathogens; the time it takes for some trees to reach a reproductive stage could outlive the careers of some scientists. However, new methods in molecular biology are overcoming these barriers these days. Understanding the process behind these pathogens will help in the prediction of their spread as well as how they may respond to climate change.
The authors also call for better management approaches that identify different classes of threat, which are defined by (i) the type of disease-causing agent (e.g. fungus, bacteria, insect), (ii) how it moves (e.g. wind, water, animal, wood imports) and (iii) the type of ecosystem service threatened (e.g. keystone species, timber value).
Management practices can also help build resilience in our forests. For example, practices that help preserve the genetic diversity of species and avoid monoculture will provide the genetic foundation that will help species resist disease. Steps to mitigate climate change may help reduce the abiotic stress on forests and reduce the expansion of pest populations.

Though there remain many unknowns and the future is uncertain, the critical role forests play globally is clear. So, if you are able, get out into a local wood or forest today and appreciate it. Those trees are cleaning the air we breathe and the water we drink. They grew that apple you brought along for a snack! They’re doing a lot as they stand there, so appreciate it…dare I even say…hug a tree?!  Who knows, you might start a trend?!
The original paper is: Boyd IL, Freer-Smith PH, Gilligan CA, Godfray HCJ. (2013) The consequence of tree pests and disease for ecosystem services. Science, 342 (6160): doi 10.1126/science.1235773
The AAAS press release associated with the paper can be found here.

Plants that endure

Posted on by andy.winfield

by Helen Roberts

Whether perched upon a windblown cliff or nestled in a small crack deep within a canyon, some plants seem to overcome all odds of survival. These survivors, which are frequently rare, quite often grow in remote inhospitable environments, show true resilience and perseverance and are highly adapted to their specific habitats. You just have to admire them for their sheer tenacity.
However, some of these ‘bulldog’ plants aren’t the hardy-looking brutes one might expect of such survivors; sometimes they are delicate and very beautiful. Discoveries of plants such as these are occurring regularly with over 2,000 new plant species being found worldwide each year. Many are found in far flung areas of the globe, as well as on our very own doorstep here in Bristol.

A Malaysian beauty

The newly described Ridleyandra chuana with a
rare two flowers. Photo credit: L.S.L. Chua
A rare and endangered endemic plant found in the biologically diverse Pennisular Malaysia has recently been described. The beautiful plant is called Ridleyandra chuana and is only found in two small mountainous areas of forest.
The plant can be simply described as a perennial herb that is somewhat woody with a rosette of dark hairy leaves at its base. It has a long slender unbranched stem with very delicate and beautiful cone like flowers, which are white with dark maroon purple stripes.
This herb grows in very challenging habitats, such as moss covered granite rock emdedded in soil or moss covered granite boulders in extreme damp and shade on steep slopes.
The maroon/purple cone-like flower of
R. chuana. Photo credit: L.S.L. Chua.
The plant was initially discovered back in 1932 at Fraser’s Hill, Pahang, but only recently have enough data been collected to formally describe the plant. It is named after botanist and conservationist Lillian Swee Lian Chua who discovered another population whilst carrying out a biological inventory of summit flora on Gunung Ulu Kali, Pahang. Because of its limited numbers (only 130 individual plants are known to exist) it has been classed as Endangered under the IUCN criteria. Of the two locations of where it is found, one location is threatened.
“The population at Fraser’s Hill falls within a Totally Protected Area and consists of about 30 plants that grow in an undisturbed site away from tourist trails and is too remote to be affected by development,” said Dr Ruth Kiew, author of the recent study describing this exquisite plant. “The other population consists of less than 100 plants at Gunung Ulu Kali, which is on private land in a hill resort that is severely threatened by road widening and associated landslips, by changes in microclimate due to edge effect as the forest becomes more and more fragmented and that is in danger of encroachment from future development. The chances of this latter population surviving is very slim. On the other hand, the rediscovery of the Fraser’s Hill population after a hundred years illustrates the resilience of species to survive if the habitat remains undisturbed.”

A beauty closer to home

Such rare and endangered plants that cling to life in the most inhospitable places are also found not too far from Bristol Botanic Gardens and are now being displayed at the Gardens as part of their ‘ex-situ’ conservation collections. The Avon Gorge, a Carboniferous limestone gorge cut out by the River Avon provides a sheltered microclimate of sun-baked niches for a wide variety of endemic species within ancient scrub and grassland communities. Many of these species are threatened by scrub invasion, introduced species and engineering works. Of these rare species, there are two endemic whitebeams, Sorbus bristoliensis and Sorbus wilmottiana that literally cling to life in the Gorge. 

They are being grown at the botanic gardens and also a number of newly discovered and described endemic whitebeams are currently being cultivated to add to the existing whitebeam collection. Wilmott’s Whitebeam (Sorbus wilmottiana) is listed by the charity Plantlife as one of our 10 most threatened woodland plants in the UK, which is why ex-situ populations are so important in helping to understand species and aid in the long term management and future development of the AvonGorge. The study and protection of rare plants is beneficial in the long run not only to the individual species, but also the plant communities to which they belong. 

Ro-botany: rotting robots in the garden

Posted on by andy.winfield

There’s something really exciting going on in the compost heap at the Botanic Garden. Don’t believe me? What if I told you that buried deep within the hot and humid milieu of the compost, lay the components of future robots that could help clean up environmental disasters such as oil spills. It might sound like a piece of science fiction, but in fact it’s part of a two year project by the Bristol Robotics Laboratory that is looking at the development of a biodegradable robot.

The aim of the project is to build a robot that is self-powered, can move and biodegrades at the end of its life.  It’s an idea that was conceived by Dr. Jonathan Rossiter from the University of Bristol and Dr. Ioannis Ieropoulos from the University of the West of England (UWE). Rossiter is an expert in the development of artificial muscles and Ieropoulos is an expert in the development of microbial fuel cells. So, when these two put their heads together to think about the future and the biggest challenges that lay ahead, they came up with the biodegradable robot.

Look out – there may be a future robot rotting in the
Botanic Garden’s compost heap!
Robots have the potential of conducting large scale clean up of the environment in order to minimize the risk to humans. However, releasing the number of robots necessary to clean up an environmental mess within a reasonable time frame isn’t currently feasible as there is too much effort required to collect them all afterwards. If the robots aren’t collected, they themselves pose a toxic threat as batteries and other components degrade and release chemicals into the environment. The solution? A completely biodegradable robot.

One obvious application of such a robot is in the event of an oil spill. “There are hydrocarbon-degrading organisms that will utilise crude oil,” said Dr. Ieropoulos, a Senior Research Fellow in Engineering Design and Mathematics at UWE. “A futuristic scenario is to release these robots with guts full of microbes that use the crude oil. The robots swim about and the microbes in the fuel cell utilise the crude oil to power the swimming action. By the time they have finished, the robots have biodegraded gracefully into that very same environment without harming it.”

The hard bits, soft bits and active bits…

The workings of a robot can be divided into three main components: 1) the stomach – where energy is generated, 2) the body – which enables movement and 3) the brain – which can receive information from the environment and potentially make decisions. For this project, Rossiter and Ieropoulos are concentrating on developing the first two components – the stomach and body.

The ‘stomach’ is a critical component of the project as it enables the robots to be self-powered. Microbial fuel cells, are a technology that uses microorganisms to directly convert organic matter into electricity.
For the body, the researchers have to identify a range of biodegradable materials: hard bits to give it structure, soft bits that act as skin to hold it all together and active bits to help it move. For this, they are looking to both human-made materials as well as biological materials (such as cellulose).

“There are two approaches really,” said Dr. Rossiter, a Senior Lecturer in the Faculty of Engineering at Bristol. “We take man-made materials that we know work as artificial muscles and see if they degrade and we take materials that we know biodegrade and see if we can build muscles out of them.”

What’s happening in the compost heap…

The researchers are looking at the behaviour of a range of biodegradable materials in different environments. They will compare how the materials decompose in the lab, exposed only to room temperature and air, with how they decompose in the compost heap, and finally how they decompose in a bacterial broth, which replicates the microbial fuel cell environment.

Each week, the materials are weighed to determine how much mass has been lost over time. The results from the compost heap will be compared with those from the lab to determine whether the bacterial broth in the lab is accelerating the biodegradation process, and if so, how much electricity is being generated through that biodegradation.

“We can feed the microbes in the fuel cell things from the environment,” said Ieropoulos, “but if there are biodegrading organisms inside the fuel cell, then at the end of the robot’s lifetime, we want them to consume the chassis and muscles of the robot itself.” 

The project began in August 2012 and will run over two years with support from the Leverhulme Trust. At the end of the two years, Ieropoulos and Rossiter hope to have a proof of concept to show that a self-powered biodegradable robot is possible.

So, next time you visit the Garden and happen to be by the compost, bear in mind that there might be a future robot lurking in there!

Through the eyes of bees

Posted on by andy.winfield

One of the many fabulous things about the Botanic Garden is that on any given day, you may find scientists out there conducting cutting edge research. There are currently at least seven research programs going on either directly or indirectly with the garden, making it not only a place of beauty, but also a place of scientific discovery.

I recently had the opportunity to speak with a researcher from the University of Bristol’s Ecology of Vision group, who was in the garden photographing flowers with the most bizarre looking camera. I generally take notice of cameras anyway, but this one could hardly be ignored. It was essentially a metal box perched atop a tripod with a lens protruding out one end and an abundance of wires to connect it to a laptop protruding out the other. It simply begged the question – “what is that and what are you doing with it?”
“It’s a POL camera,” said James Foster, a PhD student in the School of Biological Sciences, “we’re imaging the polarized light reflected off flowers. Humans don’t have polarization vision, so we use this camera to create an image that allows us to see what animals with polarized light sensitivity, such as bees, can see. We want to see what flowers are like from a bee’s point of view.”  
James Foster, a PhD student in the School of Biological Sciences,
is using a special camera, built by Dr. Shelby Temple
and Dr. Nick Roberts, to photograph flowers in the
Botanic Garden. The camera characterises and quantifies
all aspects of light polarization and will help researchers see
the flowers from the bee’s point of view.
If, like me, you aren’t confident in your understanding of polarized light, here are the basics. Light travels as a wave, oscillating as it moves through space. As it travels, the wave can oscillate in any number of orientations, up and down, side to side or any angle in between. Polarization refers to either oscillation orientation of the wave (the angle of polarization) or how many waves oscillate in the same direction (the degree of polarization).
Though humans aren’t sensitive to polarized light, many other species are, including many important plant pollinators such as bees.  It’s been known for about 60 years that bees use patterns of polarized light in the sky to navigate, but are they using polarized signals in other aspects of their daily behaviours?  This is the question Foster is trying to answer as part of his PhD.
“We know that it’s the upwards facing portion of the bee’s eye that is most sensitive to polarized light, so we’ve been looking specifically at downwards facing flowers,” said Foster. “Those that seem to be most popular with the bees are usually found as clusters on an inflorescence, often where there are less mature flowers at the top and more mature flowers at the bottom.  I don’t expect that the bee is using polarized light signals to identify the flower as a flower, but once it gets to the flowers it might be using those signals to optimize its foraging activities. For instance, it could influence the bee’s decision to stay on a lower, more mature flower that may be more depleted in nectar or move quickly up to younger flowers that may have more nectar.”
The research is still in its early stages, but if Foster can demonstrate differences in the polarized signals of mature flowers versus younger flowers that also relate to differences in nectar availability, this will be a first step in determining whether bees are using polarized signals for more than just navigation. 
Recent research conducted at the University of Bristol and the University of Cambridge, has shown that conical cells on the surface of the petals of many flowering plants help increase grip for visiting pollinators and are particularly important when the flowers are moving (as they often do in a naturally breezy world).
“Those conical cells would also reduce the degree of polarization of reflections coming off the flower,” added Foster. “What we predict is that there will be areas that will be rich in these conical cells, for gripping, but there will also be regions where the cells are completely flat and these areas will allow polarized reflections that may be important signals for pollinators.”
It’s a tricky thing trying to study a sensory world that we are essentially blind to. However, it probably means that you might see more of James wandering about the garden, POL camera in tow, trying to see the flowers through the eyes of bees.