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Invasive Plant Program

Biocontrol Cycle

Invasive Plant Assessment Stage

Extensive field work and expert knowledge of invasive plants in BC from all invasive plant managers across the province is gathered, and then entered into the Invasive Alien Plant Program (IAPP) Application for shared management and mapping capabilities.

Rank Provincial Invasive Plants Stage

The Inter-Ministry Invasive Species Working Group (IMISWG) ranks provincial invasive plants with a science-based, decision making model for determining provincial invasive plant priorities for pursuit of new biological control agents.

The Research Stage

Provincial and State agencies across North America and other countries, non-government agencies, and research scientists concerned with the biological control of individual invasive plant species form groups referred to as consortia. These consortia co-ordinate searching and screening activities in Europe, Asia and elsewhere for new agents, as well as exchange knowledge on both the invasive plants and control agents imported into new countries. One of the most important benefits of consortium membership is the efficiency gained in the shared costs and resulting biocontrol agents. British Columbia is able to participate in the international initiative to pursue biocontrol agents for invasive plant management because of established relationships based on professional trust and stable, long-term funding.

The Development Stage

Once imported into BC, this stage consists of propagating the agent and studying its habitat and handling requirements in order to provide invasive plant managers with a useful treatment tool against target invasive plants. This stage involves primary biological control agents. Primary is one of three FLNRO biological control management responsibility designations, termed primary, secondary and tertiary:

  • Primary biocontrol agents are the responsibility of Range Branch, who performs development activities with the agents.
  • Secondary biocontrol agents are also the responsibility of Range Branch, who then actively use the agents as treatment tools to manage invasive plants in the province. Other agencies may also use secondary agents as treatment tools.
  • Tertiary biocontrol agents are those that are more wide-spread around the province and are used as treatment tools by a wider range of agencies/clients when necessary, or are left to spread further on their own accord.

Range Branch receives new biocontrol agents once they pass through a federal quarantine facility. At this stage, the Ministry has a great deal of money invested in those agents and must take extreme care in handling them. It is also important to establish populations of agents shipped to BC as soon as possible as future collection in Europe and other overseas locations may be inhibited for political reasons or by encroachment on habitat by agriculture, forestry and urban development.

Primary biocontrol agent field releases are placed onto Crown land to ensure their safety and longevity of release sites. These sites are within areas given over to restoration (no longer mechanically or chemically treated) to:

  • Prevent interference from opposing treatments; and
  • Prevent the site from acting as an unanticipated seed source.

The following factors are also critical to address when placing biological control agents in the field: St. John's wort infestation

  • The infestation must be of a sufficient size to allow several generations of the agent to reproduce (>0.5 ha - depending on plant species);
  • The infestation must have a mixed age class of plants to ensure regeneration of the plant community; and
  • The infestation must not be isolated. As with other species, biocontrol agents require corridors for:
    • Movement to new sources of food/breeding if the current infestation decreases; and
    • Movement to preferable habitat.

Release of Urophora cardui galls Once field releases have been made, they must be monitored to determine if the agents have successfully established. Often little is known about the habitat requirements of these new agents following the comparison of available habitat details from the agent's native country. Following confirmed establishment, Invasive Plant Program staff collect and move the primary biocontrol agents into increasingly diverse habitats to test their limitations. Staff gather information on the life cycles and habitat preferences by studying the agents and develop techniques for collection, shipping, handling, and release procedures.

Dependent on the agent, this process can take a few or many years. The purpose of these efforts is to develop the primary biocontrol agent into a 'tool' for use by invasive plant managers. The summation of these efforts results in:

  • Changing the agent status from primary to secondary;
  • Recognition that 'early secondary' agents are still restricted in availability and handled mainly by Invasive Plant Program staff;
  • The development of a field guide book; and
  • The biocontrol agent is given over to use as a tool for management of its target invasive plant.

Field Use of Biocontrol Agents Stage

Mogulones cruciger feeding damage on hound's-tongue
Hound's-tongue
(Cynoglossum officinale)

The biocontrol agents are used as treatment tools against their target invasive plant species. Successful biological control depends on the effective distribution of the control agents. Not only can agents take many years to distribute themselves naturally, but the mountainous terrain can geographically isolate invasive plant populations in BC. Therefore, collection and redistribution are key elements to a successful biological control program. The agents may take many years for their populations to build high enough to be effective, therefore redistribution sites free of disturbance should be chosen. The application of treatments, monitoring, and particularly the recording of dispersal information from all BC invasive plant managers, is invaluable. Dispersal data is gathered in order to:

  • Further define habitat preferences; and
  • Adapt management activities.

For information on obtaining biological control agents, contact an Invasive Plant Program staff member.

Biocontrol Evaluation Stage

This stage involves the evaluation of biocontrol agent treatment, monitoring and dispersal data to determine whether the complement of agents on a plant species is sufficient. Data for this evaluation is found in the Invasive Alien Plant Program (IAPP) Application. The two main focuses of this stage are to determine whether the agents are having an effect on the target invasive plant, and whether the agents can exist in all habitats into which the invasive plant is spreading. Some trials are also conducted to address these questions. For evidence of biological control success, please go to Biological Control Success Images.

Evaluate Invasive Plant Stage

Nodding Thistle
Nodding thistle (Carduus nutans)
Considered under biological control.

This stage involves re-evaluation of the invasive plant infestations in BC by all invasive plant managers. The main factors assessed are:

  • Whether plant population density is decreasing;
  • Whether plants are affected in all habitats; and
  • Whether environmental and economic values are restored/preserved.

Data for this evaluation is found in the Invasive Alien Plant Program (IAPP) Application and gathered from invasive plant managers. If a sufficient, desired change in the plant community is achieved then the invasive plant is considered 'under biocontrol' and is left, on a provincial scale, to undergo a predator/prey cycle with its biological control agents. If the desired change is not achieved, this re-evaluation stage may result in the pursuit of new biological control agents for the invasive plant species.



"Healthy, functioning BC ecosystems, free of the impacts of invasive plants."