Biocontrol Cycle



Invasive Plant Assessment Stage

This stage consists of the collation of extensive field work and expert knowledge of invasive plants in BC from all invasive plant managers across the province. The data is entered into the Invasive Alien Plant Program (IAPP) Application for shared management and mapping capabilities.

Rank Provincial Invasive Plants Stage

This stage consists of the Inter-Ministry Invasive Plant Working Group (IMIPWG) ranking 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

This stage consists of investigating the international scientific community to enable research on biological control for specific plant species and, where possible, participating in that research to obtain agents. 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 consortiums. The purpose of the consortia is to co-ordinate searching and screening activities in Europe, Asia and elsewhere as required, for new agents and exchange knowledge on both the invasive plants and control agents imported into new countries. Membership is strictly voluntary. One of the most important benefits of belonging to these groups 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 MFR biological control management responsibility designations, termed Status, in the province – primary, secondary and tertiary:

  • Primary biocontrol agents are the responsibility of Forest Practices Branch whom enables research and performs development activities with the agents.
  • Secondary biocontrol agents are the responsibility of Range Branch whom actively use the agents as treatment tools to manage invasive plants in the province. Additional agencies 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.

MFR Forest Practices Branch (FPB) 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 by political reasons as well as by encroachment on habitat by agriculture, forestry and urban development.


Depending on the numbers, adults either are released into tents at the MFR Propagation Facility located on Agriculture and Agri-Food’s land in Kamloops to propagate and increase their numbers for later liberation and/ or they are released directly into the field. In either location, it is preferable to have outdoor facilities in order for the primary biocontrol agents to acclimatize to BC conditions and to increase in population in preparation for operational releases.



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 – dependent 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 gallsOnce field releases have been made, they must be monitored to determine if they 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, FPB staff collect and move the primary biocontrol agents into increasingly diverse habitat regimes in order to test their limitations. Staff gather information on the life cycles and habitat preferences by studying the agents in the tents and field locations 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:

  • The decision is made to change the agent category from primary to secondary;
  • Recognition that ‘early secondary’ agents are still restricted in availability and handled mainly by MFR Range Branch 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

This stage involves the use of biocontrol agents 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. Collection and redistribution, therefore, are key elements to a successful biological control program. Once at a site, the agents may take many years for their populations to build high enough to be effective, therefore redistribution sites free ofMogulones cruciger feeding damage on hound's-tongue 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.


(Cynoglossum officinale)

For information on obtaining biological control agents, contact the Range Branch staff member located in the nearest regional office.

Biocontrol Evaluation Stage

This stage involves the evaluation of biocontrol agent treatment, monitoring and dispersal data in order 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 is 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

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.

Nodding Thistle (Carduus nutans 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.

Nodding thistle (Carduus nutans)
Considered under biological control.



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