Biocontrol of southern California invasive plants

Award Period
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Agency Name
Department of Food and Agriculture
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PI First Name
PI Last Name
MSI People
Area/s of Research
Ecology and Evolution

We will continue Cape ivy biocontrol monitoring and implementation initiated with USDA-ARS, with the goal of evaluating the establishment and impact of P. regalis in southern and central California. Monitoring is intended to discern factors that promote or inhibit agent establishment along the north-south gradient, with new releases to fill geographic gaps so that we have at least one gall-fly population established in each coastal county to serve as a nursery site for cooperators to carry out future re-distribution of agents. The monitoring protocol is designed to also provide baseline conditions so that ecosystem responses to Cape ivy suppression can be documented. Field testing of D. delairea was recently initiated by USDA cooperators at limited sites in northern California and, if feasible and approved for wider cage and field trials, we will conduct corollary testing of this agent in the southern region.

Monitoring will also document co-occurring noxious weeds in or near these wetlands, such as Centaurea solsticialis (yellow star-thistle), Rhaponticum repens (Russian knapweed) and others which we would, in collaboration with CDFA, target for biocontrol with approved agents, e.g. gall-forming insects Jaapiella ivannikovi and Aulacidea acroptilonica for the knapweed and Ceratapion basicorne for star-thistle.

To gain public and agency support for this biocontrol program we will also continue, and expand upon, outreach to stakeholders with interest in or responsibility for ecosystem health in the target region.


  1. Cultivate Cape ivy plants in the greenhouse and inoculate with P. regalis to augment field releases at approved locations in central and southern California;
  2. Conduct new releases of P. regalis in counties, and approved watersheds, not currently involved in the implementation program or where prior releases have not yet lead to agent establishment;
  3. Conduct outreach to stakeholders in Cape ivy-infested watersheds of California using updated brochures, published information materials disseminated via Web-based platforms, and public presentations;
  4. Update and apply a monitoring protocol for use by our research crew, and with training by partnering organizations to document the efficacy of this agent in reducing Cape ivy abundance and facilitating recovery of native vegetation;
  5. If approval is received for wider field testing of the second agent, D. delairiensis, we will in cooperation with USDA-ARS and CDFA conduct such testing at Cape ivy-infested locations in central and southern California, emphasizing locations where P. regalis is not yet established to avoid complications of dual releases at this stage;
  6. Participate with CDFA in maintenance, release and monitoring of approved agents against regional invasive pest plants that may increase following Cape ivy suppression.