Biological control agents and host plants

Invasive plant species targeted in B.C. have been introduced from other continents, primarily Europe and Asia, and have no natural enemies to attack them and keep them under control. Biocontrol research and thereafter management efforts reunites these invasive plants with their natural enemies by importing agents, mainly insects, that feed on the plants from the native habitat. Release of biological control agents into British Columbia began in 1951 with the introduction of Chrysolina quadrigemina (Suffrain) and C. hyperici (Forster) to control St. John's wort (Hypericum perforatum L.) [1]. As of February 2020, B.C. has records for 87 separate species, or 89 if strains of species are considered as separate biocontrol agents, having either been purposely introduced (72) or having found their way into the province (17) to target 38 invasive plants. Establishment of the purposely introduced species in B.C. is at 74%, which is higher than the average of about 60% reported for classical invasive plant biocontrol agents released elsewhere in the world [2], and even the average of 70% recorded for agents released in western Canada [1]. In few historic occasions, and in current rare circumstances, natural predators have been able to follow their hosts into new habitats. These adventive insects are described:

• Adventive Biocontrol Agents 2022 (PDF, 67KB) 

References

[1] De Clerck-Floate, R. and H. Cárcamo. 2011. Biocontrol Arthropods: New Denizens of Canada's Grassland Agroecosystems. In Arthropods of Canadian Grasslands (Volume 2): Inhabitants of a Changing Landscape. Edited by K. D. Floate. Biological Survey of Canada. pp. 291-321.

[2] McFadyen, R.E.C. 1998. Biological control of weeds. Annual Review of Entomology. 43:369-393.

The table below lists invasive plant species and their biological control agents.

* The monitoring/dispersal Biogeoclimatic Ecosystem Classification (BEC) zones listed as positive for biocontrol agent survival include those where monitoring has been performed and the agent has been found. This information does not necessarily preclude the possibility of the biocontrol agents establishing in additional BEC zones.

**The categories and their definitions for the 'collectability' of biocontrol agents in B.C. are as follows:

• No federal permit: Host-specificity tests were not performed and a federal permit from the Canadian Food Inspection Agency (CFIA) was not obtained to import these agents into Canada. These agents are typically adventive. For more information see the Adventive Biocontrol Agents document and the text included on the bioagent page to determine whether the agent may/should be collected and redistributed
• Not established: Repeated monitoring has revealed no sustained population of a released agent
• Not available for general distribution: Agents that have been released, but are still under study in development as treatment tools. Historically, these agents were described as ‘primary’ in B.C.
• Limited: Agents that are regularly establishing and exist as treatment tools but for which collection numbers are low, typically in the hundreds for any given site in a season. Historically, these agents could be described as either ‘secondary’ or ‘tertiary’
• Mass: Agents that are present and exist as treatment tools and for which collectable numbers are typically plentiful, in the thousands, for any given site in a season. Historically, these agents could be described as either ‘secondary’ or ‘tertiary’
• Passive distribution: Agents that are difficult to collect because of their biological traits, or they exist in low densities and therefore are left to self-distribute on their target invasive plant. Note: agents that become wide-spread due to collection and redistribution efforts may thereafter be left to passively redistribute further. Historically, these agents would often be described as ‘tertiary’