Click here for Carrick Invasive Species Project (CISP)

Invasive Weeds are increasingly becoming recognised as an environmental and economic problem throughout the UK.

Giant Hogweed1

Three main species are recognised as particularly detrimental including Giant Hogweed, Japanese Knotweed and Himalayan Balsam. In 2008, ART commenced a survey of these species on Ayrshire rivers and undertook an eradication programme for Giant Hogweed on the upper River Ayr.

Giant Hogweed is a particularly dangerous plant that can cause severe burns and blisters to humans when their skin comes into contact with the sap of the plant.

The Project includes surveys of invasive weed distribution on the main watercourses in Ayrshire. The Rivers Irvine, Ayr and Girvan were mapped during 2008 and the Stinchar, Doon and Garnock are almost complete at the time of writing (August 2009).The results are detailed in the maps available on this site. More detail is available from ART. Due to the ever changing distribution of invasive weeds these maps represent the distribution at the time of survey and will be updated as and when required. ART cannot be held liable for omissions or errors that may occur.

Himalayan Balsam

We presently have two funded initiatives:

  • CIRB covering north Ayrshire
  • CISP covering south Ayrshire

See the Invasive Weed Distribution Maps here.

Inappropriate methods of control include strimming, cutting and excavating, all of which may lead to the rapid spread of plants. ART can advise landowners on best practice when dealing with these species. Contact either Stuart, Gordon or Meryl for assistance.

Please click on the following pdf link for a copy of advice to control the invasive non native weeds in a river environment.

Advice for controlling Invasive Weeds.pdf (647Kb)

For all species near watercourses, application of chemicals must be approved by SEARS (Scottish Government) prior to commencement. The application form is available by clicking here and submission is free.

In 2008 ART undertook experimental control of Giant Hogweed on the River Ayr upstream of Stair Bridge. This trial continued in 2009 and has been highly effective. During 2010, ART continued with their control on the upper River Ayr, but additionally extended control to public areas in the lower river on behalf of South Ayrshire Council. The Pow Burn, Ladykirk Burn and another connected but un named burn were also brought under control by Trust staff. Himalayan Balsam within the Doon catchment was also targeted which was possible due to funding received from SEPA’s restoration fund and the Doon Salmon Fishery Board. Japanese Knotweed will also be targeted during Autumn 2010 on the Doon, again possible due to contributions from the same organisations. The Rivers Irvine and Girvan have also benefitted from ART’s commitment to control/eradicate these invasive species. Early in 2010, ART trained volunteers from angling clubs in the safe use of pesticides and during the season, these volunteers have actively been targeting their local waters with good results. Anyone interested in participating in future training and invasive weed control should contact the Trust.

Further funding has been applied for that will allow the control of this plant along the length of the Rivers Ayr, Annick, Irvine and Garnock.

Members of the public with information on any of these weeds are encouraged to contact the Trust. By mapping their distribution, it is hoped that strategic control measures can be implemented and the spread of the weeds halted.

ART staff are qualified and always willing to provide advice and guidance on invasive species control. Don’t hesitate to get in touch if you would like our assistance.

The sap from this plant is dangerous to humans reacting with sunlight and causing severe blistering and recurring dermatitis. Consequently, no attempt should be made to strim plants. Mowing can also be dangerous and in general should be avoided.

Recommended methods of control.

  1. Spraying using knapsack sprayer and systemic, glyphosate based herbicide. Roundup Pro Biactive is widely accepted as the most effective chemical suitable for use near watercourses. Only approved pesticides will be acceptable to SEARS who issue spraying licenses. Application must be by qualified person only. (PA6AW is the required standard).Timing of spraying is important. Too early and many plants won’t have emerged from the soil. Too late and plants may already be flowering or developing seed. Our experience in Ayrshire indicates that late March/ April until early June is usually an ideal time to spray however this year (2010), due to the prolonged hard winter, it is likely that spraying will be delayed by around 1 month. Plants should be around 18″ (0.45m) tall when sprayed. Care must be taken to ensure that plants are sprayed using the appropriate strength/dilution and that the whole plant is sprayed. (when plants receive less than a lethal dose, they often survive and develop flowers prematurely as a stress response.)
  2. Cutting stems only delays flowering. For cutting to be effective, the plant should not have flowered and the root should be cut through at least 50mm below the soil surface. This method is only suitable where an individual plant occurs or where chemical application is not possible. Anyone cutting GHW should wear adequate personal protective equipment and be aware of all emergency procedures to follow should contact with the plant occur.This method should only be used as a last resort.
  3. Grazing. Grazing is not a substitute for other treatments but it may be used in certain circumstances to assist in control.

ART staff are qualified and always available to advise on chemical control methods.

Himalayan Balsam is an annual plant that reproduces from seed. As the seed pods ripen, they explode spreading the seeds for up to 7 meters.

Recommended methods of control.

  1. Spraying using knapsack sprayer and systemic, glyphosate based herbicide. Roundup Pro Biactive is widely accepted as the most effective chemical suitable for use near watercourses. The main disadvantage to using herbicides to control any invasive weed is the unavoidable application to native plants growing in the immediate vicinity of the target species. Consequently, spraying is only recommended where HB forms large dense stands and prior to flowering.
  2. Strimming and mowing of HB is effective but only prior to the seed pods developing. Any attempt to cut this plant once the seeds have developed will cause the seed pods to burst, spreading the plant. Strimming can be performed from spring to around early July.
  3. Manual pulling. This is a slow technique only really suitable for low density infestations. Pulling should be performed prior to the formation of seed pods. The plant should be uprooted if possible as this ensures that new shoots can’t develop. This method is highly suited to dealing with initial outbreaks of the species.

As HB is an annual and its seed viability is thought to be around two years, it can be eradicated in a relatively short period of time with sufficient effort. Strategic control from the upstream limit would be required to achieve this goal.

JK reproduces only from cuttings, not from seed. It is therefore essential that those involved in Knotweed control take great care to prevent cutting or breaking plant stems or roots.

Recommended methods of control. There are only two control methods suitable for use in a riparian situation.

  1. Spraying using knapsack sprayer and systemic, glyphosate based herbicide. Roundup Pro Biactive is widely accepted as the most effective chemical suitable for use near watercourses.Timing of spraying is important with the best results achieved during autumn when the plant has developed flowers. Both the top and underside of the leaves should be sprayed before the plant starts to die back for winter. The weed killer is translocated to the roots killing the plant from the ground up. Any re-growth the following Spring should be treated using the same methods. Ongoing monitoring of treated stands is essential as this weed can be extremely persistent and difficult to kill. In all instances, it is likely that more than one application of glyphosate will be required to kill the plant however the impact and biomass of the plant can quickly be reduced using the described methods.
  2. Stem Injection is a relatively new technique that is proving to be highly effective in destroying JK. It relies on specialist equipment to inject a measured dose of herbicide into individual JK canes. It is most suitable for use in small stands of the plant.

Under no circumstances is cutting or strimming JK recommended as this only serves to spread the plant. This method also raises the problem of dealing with the cut material which becomes a controlled waste and must be sent to a licensed landfill facility willing to accept this waste. Leaving the cut material to decompose in situ is not acceptable as it can re-grow thereby increasing the problem.