Cooperative Fish and Wildlife Research Units Program: Washington
Education, Research and Technical Assistance for Managing Our Natural Resources

Washington Project

Restoration tools for Oregon silverspot butterfly

May 2018 - September 2020

Personnel

Participating Agencies

  • SSP
Oregon silverspot butterfly, Speyeria zerene hippolyta, is at great risk of extinction with only five remaining populations due to extensive habitat loss on the coast of Oregon, Washington and Northern California. Despite decades of captive rearing and reintroduction, remaining populations continue to spiral downward with increasing risk of imminent extinction. Efforts to recover the butterfly require aggressive habitat management and restoration to recreate habitat in the wild and begin the road to recovery. A major barrier to habitat management is aggressive invasive species which radically change the structure of the plant community. Critical to Oregon silverspot is early blue violet, Viola adunca, the butterfly’s larval hostplant. In coastal prairies, violets are overtopped by invasive forbs such as false dandelion, Hypochaeris radicata, and tall perennial grasses such as velvet grass, Holcus lanatus. Selective use of herbicides provides one promising tool to rapidly reduce invasive plant species, but effects on Oregon silverspot are unknown.

USFWS plans to reestablish populations of the severely endangered Oregon silverspot butterfly on two National Wildlife Refuges (NWR) in Oregon and Washington. Maintaining suitable habitat for Oregon silverspot is challenging. Oregon silverspot larvae need high densities of their host plant, early blue violet to develop into adult butterflies and the violets are an early successional species that is outcompeted by invasive plants. The project goal is to support refuge managers in deciding whether two selective herbicides should be used to maintain native prairie in the presence of Oregon silverspot. As part of the project, laboratory research will be conducted, and a management model will be developed to inform managers of the impacts of treatment with herbicides on Oregon silverspot viability.

Research Publications Publication Date
Doll CF, SJ Converse, and CB Schultz. 2022. Non-target effects of herbicides on the Zerene silverspot butterfly, a surrogate for the Oregon silverspot butterfly. Journal of Insect Conservation 26:1-15. January 2022
Presentations Presentation Date
Doll CF, SJ Converse, and CB Schultz. 2019. Evaluating non-target effects of herbicides on Zerene fritillary (Speyeria zerene zerene), a surrogate for Oregon silverspot (Speyeria zerene hippolyta). Entomological Society of America Annual Meeting, St Louis, Missouri. 17-20 November. November 2019