Gray-tailed voles are a recurring pest in Oregon agriculture and can cause serious crop damage when populations surge. In the Willamette Valley, grass seed fields provide prime habitat.
By identifying shared priorities and strengthening collaboration, the summit created a clearer path toward better vole management, more effective research investments and practical tools for growers.
The grass seed industry reported an estimated $35 million to $50 million in losses during recent years with high vole populations. These outbreaks cut yields, increase labor demands and add stress for growers working to protect crops and livelihoods.
Like many vole species, gray-tailed voles follow population cycles. Numbers can rise sharply every four to eight years before dropping again. From 2020 to early 2023, damaging populations persisted before finally declining.
Growers had limited tools to respond. Zinc phosphide baits were the only rodenticide registered for use in grass seed fields. Researchers also lacked efficient ways to measure vole populations and crop damage. That made it difficult to test and compare management options.
These gaps highlighted the need for coordinated research, practical guidance and stronger collaboration.
In response, a multidisciplinary team organized the inaugural Willamette Vole Summit for Aug. 29, 2025, in Salem. The summit brought key groups together to set shared priorities.
The summit was hosted by the Oregon Grass Seed Commissions in partnership with Oregon State University Extension Service, the Willamette Vole Management Group and the U.S. Geological Survey Oregon Cooperative Fish and Wildlife Research Unit.
Participants included those most affected by vole damage and those working on solutions. Attendees included growers, industry representatives, regulators, academics and researchers from state and federal agencies.
Nearly 100 people attended, including growers, industry representatives, researchers, government staff, legislators and OSU Extension employees. Organizers also worked to include a broad mix of stakeholders, such as small-acreage farmers, OSU Extension Master Gardener volunteers, nursery and landscape professionals, commodity group representatives, agronomists and regulators.
The summit had two goals: review current research on vole management and identify research priorities for Oregon.
Participants help shape priorities
The summit opened with presentations on recent and ongoing research. Participants then joined facilitated roundtable discussions. They shared experiences, discussed control efforts and identified needs for research and management.
Roundtable discussions showed that vole outbreaks affected participants in three main ways: health and safety, finances, time and health.
Reported losses ranged from acres of vineyard damage to yield losses of as much as 50% in a single crop. Growers also described significant time spent monitoring fields and attempting control.
Participants emphasized that vole damage affects more than yield. It also disrupts farm operations, complicates decision-making and affects the well-being of producers and workers.
Research priorities emerge
Participants identified four research priorities: better understanding vole ecology and population cycles; evaluating reproductive disruption and fertility control methods; clarifying the role of predators and habitat; and improving rodenticide options.
They also identified what is needed to adopt new solutions. These needs include funding for research and on-farm trials, clear evidence from peer-reviewed studies and stronger partnerships among growers, researchers, registrants and regulators.
The summit provided clear direction for future work and helped define the role of the Willamette Vole Management Working Group. Organizers summarized the discussions in a report shared with participants.
The meeting also generated practical ideas to guide next steps in research, outreach and collaboration.
Public value
This effort helped OSU Extension bring together the people and institutions needed to address a costly agricultural problem.
By identifying shared priorities and strengthening collaboration, the summit created a clearer path toward better vole management, more effective research investments and practical tools for growers.
This work helps reduce crop losses, improve returns on public and private investments and support the resilience of Oregon agriculture.
