Cam Valley Forum Volunteer clearing Floating Pennywort, photo courtesy of Cam Valley Forum
Floating Pennywort can be found on the Cam, Gt .Ouse, Lark, Bourne Brook and the Old West. Fragments of plant detach from existing rafts of the weed and float downstream to catch on overhanging trees and vegetation and where they will start to growth. Boats definitely play a role in spreading plant fragments but the case against water birds is less certain. Interestingly it is not as widespread on the Cam as it flows though the centre of Cambridge. This is thought to be because the plant fragments appear to prefer “sticking to” natural vegetation or obstructions – the banks of the Cam in the city centre are hard piled and smooth and don’t seem to be very attractive to the plant. This may have serious implications about how banks and overhanging trees are to be managed – some tough choices ahead perhaps?
The riparian owner is ultimately responsible for the control of the plant if it is not on a main river. Environment Agency permissive powers allow the Agency to gain access for removal to other watercourses if it poses a risk to flooding or navigation on main rivers.
Control methods in Cambridgeshire so far…
- Rakes : Cam Valley Forum Volunteers have been holding regular working parties to clear the weed from the Cam. They have found the type of rake used to be important – the tines needing to be curved and close together. Booms are put in place to prevent small fragments floating downstream. The main problem with this approach has been accessing the plant where there are overgrown and steep banks. Disposal has also proved tricky due to its bulk and weight. It can be composted under a tarpaulin but can live up to a month like this before it dies. There have been varying reports about whether cattle will eat it or not, some do, some don’t!
- Mechanical weed cutting: used by the Environment Agency and Cam Conservators. The latter have been clearing Floating Pennywort for about 8 years when it first became a menace. Again, the use of a boom to prevent fragment dispersal is important.
- Herbicide: varying levels of success have been experienced using the herbicide glyphosate as the chemical appears to have little/no effect on submerged plant parts. Best results have been achieved by spraying when the plant is young in early spring and adding Topfilm – a naturally based aquatic adjuvant approved for the use in the control of aquatic weeds. This improves the way the herbicide “sticks” to the leaves. It has been found that the plant needs to be sprayed every 3 weeks when it is growing strongly and when temperatures are above 6⁰C with control taking up to 8 weeks. Problems arise when the weed has got into the natural bank vegetation – spraying to kill the weed will also kill the bank vegetation, winter spraying when the native vegetation is dormant but the Pennywort is still growing is an option. Cam Conservators have found an integrated regime of mechanical removal, followed by hand picking and then herbicide use has given the best control so far.
The future – harnessing the power of weevil…
CABI (Centre for Agriculture and Biosciences International) have identified a South American weevil (Listronotus elongatus) which may have potential for biological control of the weed. The weevil larvae mine into the stems and the adults eat the leaves of the Pennywort. At present, indications are that it is specific to Floating Pennywort and can survive colder temperatures. Extensive tests have been carried out to ascertain its effectiveness and safety which have been submitted to the UK regulators who are now considering its suitability for release.
Listronotus weevil , photo courtesy of CABI
Earlier the year I attended an excellent workshop about Floating Pennywort hosted by Cam Valley Forum & Cambridge Conservation Forum. Below are some of the facts I gathered about this menace which is plaguing the Cam, Ouse and various Lodes in the area. Part 2 will be about the control methods currently in use and what may be available in the future.
Why is it such a pest?
All down to biology ….
- The plant has an amazing ability to reproduce itself, not by making seeds but by shedding parts of its stems which contain growth points called nodes – these nodes have the ability to start growing roots and shoots all over again. It is estimated that a square metre mat of the plant contains approximately 2,300 nodes, all of which are capable of regenerating new plants. The broken off plant parts can float
|You can see the roots starting to grow at the nodes along the stem.
Photo credit: GB NNSS
2.It was bred by the aquatic nursery trade to be a vigorous spreader – which they successfully achieved. It can easily out-compete most native plant species.
3. It is not fussy about nutrient requirement and has no limiting nutrient level. Whatever nutrient it can find it tends to scoop up and high levels of toxic elements such as mercury have been found in plants in the Netherlands
4. It is frost tolerant and needs a good hard spell of freezing weather to stop growth. Frost will kill the top growth but the growth underwater may survive.
5. It doesn’t move (translocate) herbicides well to its leaves and stems and to really kill it off the apical (end) bud needs to be sprayed. A plant will survive a spray if the apical bud is under the water or is “hiding” on a non sprayed bank side. It can take up to three weeks for glyphosate (the herbicide used in control) to take effect.
6. In the south of the country it has started to set seeds; this could be due to warmer weather or more worryingly, species adaptation.
Next week: how it spreads and how it is currently being controlled in Cambridgeshire
Community flood volunteers and flood groups are key in helping their community to be prepared for flooding and other emergencies. They play a vital role in a community’s response before,during, and after a flood.
Working in partnership the Environment Agency, Cambridgeshire Fire & Rescue, Cambridgeshire County Council, Peterborough City Council and Anglian Water are offering 2 free training sessions for all new flood volunteers and those communities who are interested in setting up flood volunteers in Cambridgeshire and Peterborough.
You don’t need any previous experience. You just need to be willing to learn how to help your community.
By attending the training, you’ll gain an insight into the work of the Environment Agency and its partners. During the day you will cover modules in:
– Role profile: what do community volunteers do?
– Introduction to emergency services: what they do and don’t do.
– Understanding flood risk: an introduction to flooding, responsibilities of organisations
and flood warnings.
– Flood risk awareness: personal safety and dangers of flood water
– Equipment: how to use hydrosacks and the correct use, maintenance and storage of
high visibility clothing and equipment.
The dates of the 2 training sessions are: (Please note you only need to attend one of these dates)
Wednesday 29th November
10:00 – 16:00
Cambridgeshire Fire and Rescue Headquarters
Friday 1st December
10:00 – 16:00
Environment Agency Office
To get the most out of the training course places are limited to 30 attendees for each day. Places will be allocated on a first come first serve basis and a maximum of two representatives only from each community can attend.
If you would like to book your place please email Tamsyn.Ellway@environment-agency.gov.uk or call 020 302 51949 with your 1st and 2nd preference for which training session you would like to attend.
Calling all Ramsey Litter Heroes, your local river needs you!
On October 17 there will be a litter pick behind the George Hotel in Ramsey – anyone with enthusiasm for wildlife, nature and improving the environment is welcome. We will start at 10.30 am and will be finished by midday. All equipment will be provided. The morning will be run by RiverCare and Cambridgeshire ACRE.
RiverCare supports volunteer groups to adopt and look after a stretch of river near to them. The looking after bit begins with holding litter picks; litter is a real threat to our wildlife in and around our rivers and contributes to the spiralling pollution of our oceans.
If you are interested in coming along please contact Rachael Brown on firstname.lastname@example.org , 01353 865037 or visit the Events on Cambridgeshire ACRE’ s Facebook page. We need to know numbers to make sure we have enough equipment on the day.
Looking forward to seeing you there!
There will be a number of drop in events taking place this summer for the public to find out more about the impending works on the Middle Level and South Level Barrier banks due to start this July. For exact dates and venues see Ouse Washes Newsletter – June 2017
The 2017 Catchment Report and Action Plan for the Old Bedford including Middle Level Catchment can be found here .This plan is a working document and will be updated on a quarterly basis. Our next step is for catchment partners to prioritise the issues identified and develop actions/programmes of work based on these priorities.
The terms of reference for the Partnership are here.
Tuesday 8 March
You are invited to a free farm walk and talk at Flegcroft Farm near Whittlesey on Tuesday 8 March. The day starts at 10am. To register contact Andrew Down on 07769 305472 or email@example.com and quote the reference AD3. Lunch included.