Mervyn Newman and Peter Nicholson
Natural England Environment Agency
Cornwall County Council
Tamar Valley National Landscape
•Giant hogweed
•Japanese knotweed
•Himalayan balsam
•American ‘skunk cabbage’
• Can only get worse
• The sooner it is started the sooner under control
• Helping landowners directly is likely to give better results
• This could be the basis of a new project as most people would be accepting of help to deal with this plant
• Landowner contributions could be suggested to help defray costs
• Swansea work shows the way: 1 treatment with Glyphosate per year at full leaf. This could be in (June), July, August, September or (October)
• Do not use stem injection by watercourses as it uses 15x the amount of herbicide used in spraying
• Ask EA to agree to one licence for the whole river (cf R.Tweed)
• Organic sites can still be helped in a variety of ways
• Cornwall County Council are dealing with 2,500 JK sites on their side of the river!
• Devon County Council needs to catch up
• Trial the Sap-Sucking Psyllids from CABI
• Consider training local volunteers to herbicide ticket standard.
• Access routes will need to be made and kept open to allow for herbicide application. This can be winter work.
• Raise awareness of damage done in mowing, cutting, hedge trimming JK.
This Act refers to the landowner or occupier which they define:
“occupier” means in the case of any public road, the authority by whom the road is being maintained]
• There are clearly several hotspots
• Some of these have been dealt with ie. on R. Carey
• Others have not
• Morwellham has 1000s of plants
• The River Lyd has 450 skunk cabbage
• Many of the mature plants are in silted backwaters from where they could be removed by digging.
• Spraying will take time to achieve full results as the mature plants hide other plants and seedlings.
• Either digging out or spraying will require ongoing monitoring by people familiar with their river stretch as the young plants will be difficult to spot.
• Detrimental shading effect as the tallest annual present in the UK
• Himalayan balsam takes advantage of nutrients lost to the river and its silts growing even taller
• Larger plants will throw more shade and produce more flowers and seeds and be able to eject them further from a greater height
• Its highly attractive nectar distracts bees and other possible pollinating insects away from native plants which may fail to get cross-pollinated.
• Insubstantial root system leading to greater bank erosion
• Increased water turbidity inhibits aquatic plant growth limiting oxygenation of the water and reducing the chances of shelter for insects and fish
• Reduced aquatic plant growth limits the ability of channelling water flow between plant clumps that cleans the gravels that are potential fish spawning areas
• Degradation of the dead plants then takes oxygen from the river on decomposing and releasing nutrients into the river on its breakdown
• Allelopathic interference with roots and mycorrhizal networks of native plants/trees (OP Smith, 2013) (R Ruckli, 2015) (Bieberich J et al, 2018)
• The high concentrations of phytotoxic alkaloid naphthoquinone from the extra-floral nectaries as well as from the nectaries, leaves and roots are likely to be damaging to aquatic environments with both phytoplankton and zooplankton (e.g. Daphnia sp.) potentially affected (Jens GP Diller et al, 2022)
• The loss or change of season of native plants has a knock-on effect to insects and thence to insectivores, omnivores or carnivores like trout
• Disadvantage to bees from the rich/quick nectar ingestion and to hive by providing late season honey crop instead of storing food for winter
• Disadvantage to bees’ health from reducing the variety of plant species that they use (Gonzalez FN et al, 2024)
• Likely transmission route for the varroa mite Varroa destructor and its associated detrimental bee viruses such as Deformed Wing Virus (DWV) and Acute Bee Paralysis Virus (ABPV) (Najberek K et al, 2023) (PA Burnham et al, 2021)
• High visitation rate to Himalayan balsam flowers (Vervoort A et al, 2011) and siting of anthers above the flower’s entrance increase the likelihood of transfer of varroa mite to the flowers and so between honeybees and hence between hives but also to wild bee species and bumble bees
• Possibility of transfer of viruses and parasites between bees of the same and different species via the much-visited balsam flowers
• Possible transfer of fungal pathogens to agricultural crops including wheat, forage maize, grapes, tomato, courgette and cucumber via the balsam flowers. One study found that two of the most dangerous fungal pathogens, Botrytis cinerea and Fusarium graminearum were facilitated in their transmission by Impatiens glandulifera invasion potentially decreasing crop production and increasing economic losses (Najberek K et al, 2023).
Section 23 of the Infrastructure Act 2015, which received Royal Assent on 12 February 2015, amends the Wildlife and Countryside Act 1981 by inserting a new Schedule 9A to introduce a new statutory regime of species control agreements and species control orders to ensure that landowners take action on invasive non-native species or permit others to enter the land and carry out those operations.
Wildlife and Countryside Act 1981 Schedule 9a
(a) species control agreements between environmental authorities and owners of premises, and
(b) species control orders made by environmental authorities, and for related matters.
