Control and Management
Guiding principles on control and management
Where invasive alien species have been introduced and establish self-sustaining populations, eradication may no longer be possible or feasible. Many invasive species that have established populations in Ireland can cause significant damage to our natural environments and wildlife. Taking action to contain, control or manage these populations to limit their spread or reduce impact may be required. A range of good practice management guides and Invasive Species Action Plans can be found on our Resources page.
While all invasive species have specific control and management requirements there are some overarching principles that apply to all species which can help to guide the development of action plans . These overarching principles are outlined here.
1. Ensure correct identification. This is an essential first step to confirm the suspected invasive species identity before any action is taken. The outward appearance of some invasive species can be surprisingly similar to many of our native plants and wildlife. Making sure that the species in question has the key identifying characteristics of the suspected invader is extremely important. To assist in your identification, invasive species ID guides can be found here. Your invasive species sightings can be recorded on our website here or reported directly to relevant authorities. Where possible expert validation of your record should be sought.
2. Get to know the invasive alien species. Gathering information and resources on the invasive alien species of interest can provide important insights on aspects of their biology and ecology. With this you can understand what makes the species so successful in their invaded range. This can also help to identify vulnerabilities in an invasive species life cycle that may be exploited at specific times (e.g. during periods of die back/die off). It can also highlight times or points in the species life cycle when action may be ill advised (i.e. during a species active reproductive phase – seed or larval release). To inform management actions, it is important to gain an understanding of:
- The capacity of the species to persist in natural environments.
- The specific traits which facilitate invader success.
- How the invasive species achieves secondary spread, locally and regionally (e.g. through wind dispersal, creeping roots, fragmentation, watercourse dispersal, parasitism, human or animal mediated spread).
- The growth and reproductive cycles of the invasive species.
- The susceptibility or resistant (i.e. the response) of an invasive species to different control treatments.
- The impacts of the invasive species on wildlife and the functioning of the natural environment of the site or surrounding location.
- The interactions between different invasive species. Where more than one invasive species is present on a site they may facilitate or inhibit the spread or growth of the other.
Gathering this information will help to develop and inform robust control and management actions. To learn more about the invasive species you would like to management you can use visit our invasive species identification guides here and good practice guidelines here which provide details on invasive species traits, impacts and management.
3. Get to know your site. Understanding the characteristics of an invaded site are important for managing invasive species. Certain characteristics of the site might explain why and how the species arrived, if future introductions are likely, how effective any control or management actions may be and if there are any facets of the site which might impede or facilitate action. Key aspects which will help you understand you site prior to taking action include:
- Identifying key features of the site will inform management and control actions. Natural boundaries such as hedgerows or watercourses can act as barrier which can limit the spread of invasive species. In some circumstances they may also facilitate spread or have facilitated the initial arrival of an invasive species on to your site. The role that natural boundaries play in invasive species action plans will largely depend on the targeted species, their traits and ecological requirements.
- Understanding the distribution and abundance of an invasive species on your site will help you to devise a targeted and strategic control programme and where efforts should be directed first (e.g., targeting dense aggregations or those at the periphery or boundary of the site).
- Understanding how long the invasive species has been present on the site will inform the level of effort that may be required and the capacity for the species to re-establish. For example, many where an invasive plant species has been present for several years, they may have built up a seed bank and could therefore easily re-establish despite control and management efforts.
- Understand where your site sits in terms of the wider landscape. This will involve understanding its connectivity with other sites, its proximity to likely transport corridors or pathways. If your site is a designated protected area or adjacent to a protected area careful consideration and engagement with relevant authorities will be necessary. This will also be necessary if your site or the surrounding area is a habitat for protected species.
- Determine whether any other invasive species are present on the site and where multiple species co-occur the control programme should consider whether both species can be targeted or if management actions for one invasive species might facilitate the spread of another. For example, if an area is cleared will this provide an opportunity for another invasive species to establish.
- If the invasive species is present in adjacent areas, consider contacting other landowners to co-ordinate control and management actions.
4. Set an end goal. Clearly define the goals of the control and management plan by identifying key priorities for taking action. Priorities could include:
- Protecting or reducing specific impacts on the natural environments and native wildlife.
- Protecting buildings or structures.
- Clearing to facilitate movement through areas or to promote the reestablishment of native plants and wildlife.
- Containment to restrict the distribution of an invasive species and prevent spread to other natural areas or habitats.
Understanding the key priorities of planned actions will help to determine what actions need to be taken and whether they are likely to bring about desired results in the short, medium and long term. Defining the goals of planned actions early in the project will also help to determine whether the goals are achievable and realistic with the resource that are available.
5. Decide on and evaluate planned actions. Once you have gained an understanding of the invasive species, your site and clearly defined your goals for management, an invasive species action plan can be devised and evaluated. This should also establish the who, what, where, when, how and why of the control and management plan. This plan will need to:
- Understand the resources and commitment required over the life time of the management plan (i.e., in the short, medium and long term).
- Determine the timescales for the planned control and management actions.
- Consider maintenance, monitoring and restoration into the future (this will depend on the goals of the action plan).
- Consider the health and safety of planned actions and carry out a risk assessment for the project. Where the use of equipment, machinery or chemicals forms part of the action plan carefully follow manufacturer/safety guidelines. Determining whether the invasive species poses a risk to health and safety should also form part of the risk assessment. Preventative or remedial action to reduce the identified risks should be outlined.
- Consider whether specialist contractors or experts are required to carry out planned actions. This may be necessary where specialist equipment is required, or treatment methods pose a significant risk and specialist training to handle or manage this risk is needed.
- Consider how to safely handle and dispose of invasive species to reduce the risk of accidentally spreading the invasive species.
- Review and evaluate whether the planned actions will meet the primary objectives/goals for the project and always assess their impacts on non-target environments and species.
- Always adhere to best practice, ensure the information you gather is from a reliable source.
- Ensure that you have obtained any necessary permissions from relevant authorities before taking action.
Types of Control and Management
There are three main types of invasive species control methods. These are biological control, chemical control, and physical/mechanical control. Selecting the correct form of control will depend on the target species. Often invasive species are managed using a combination of different control and treatment types. Integrating multiple forms of control can offer a more effective, economic and sustainable way of managing invasive species.
Biological Control – this form of control uses natural interactions between different species to limit the abundance of an invasive species.
- Involves the use of a species ‘natural enemy’ to substantially reduce the abundance of an invasive species population.
- A ‘natural enemy’ generally originates from the same location as the invasive species and generally has a shared evolutionary history. This often means that the natural enemy has developed specific traits which allow it to prey/feed on or otherwise inhibit the invasive species in question.
- Natural enemies can be predators, herbivores, parasites, or pathogens.
- ‘Classical biological control’ differentiates itself from general biological control as it specifically involves the use of insect herbivores to control invasive plants.
- Insects used for this form of invasive species control are ‘specialist’ rather than ‘generalist’ herbivores (i.e. they feed on one specific plant species rather than a range of plants).
- Classical biological control agents go through rigorous laboratory trials and population modelling tests before being considered for release into natural environments.
Chemical Control – this form of control uses chemical solutions to actively reduce the growth or abundance of invasive species.
- Involves the use of biocidal treatments with active agents to induce death or significant degradation of targeted invasive species.
- For example, chemical treatments can include bleach, vinegar, Virkon products, lime, fresh or salt water, among many others.
- The method of application of these treatments (soaking or spraying), concentration of solutions and the regime of treatment (i.e., duration of soaking, frequency of application, intervals between treatments etc) are important factors when determining their effectiveness.
- Where invasive species are present in commercial industries broad spectrum herbicides and pesticides are often used to control both invasive and native pest species.
Physical/Mechanical – this form of control involves the physical or mechanical removal of invasive species (e.g. removal by hand, air drying or using equipment/machinery).
- Involves simple methods like hand removal, cleaning with hard bristle or wire brushes, air/water blasting, desiccation (air drying) as well as the use of physical barriers such as biodegradable geotextiles and plastic wrapping to smother targeted invasive species.
- V-blade cutting can be used to remove dense stands of invasive aquatic plants from waterbodies.
- Desiccation through air drying can be an extremely effective way of controlling invasive species. However, this treatment can vary in its effectiveness as temperature, humidity and light exposure can influence the time it takes to completely dry equipment, gear, and leisure/commercial craft. Many species can survive for more than two weeks in damp conditions.
- Physical/mechanical removal can be labour intensive and cost prohibitive where invasive species have established extensive populations.
The National Biodiversity Data Centre does not undertake practical control on the ground nor are we an advisory body on control. However, these details and resource links may help guide your actions.