- Animals: sheep
- Pest Management: biological control, integrated pest management
Spotted knapweed is an extremely aggressive competitor that threatens the ecological sustainability of western rangelands and economic sustainability of western ranches, animal production systems, and rural communities. In response to the high costs, environmental concerns, and health risks associated with herbicides, landowners and land managers have explored the integration of biological control and targeted (or prescribed) sheep grazing on spotted knapweed invasions. It is unknown if sheep grazing decreases the insects’ efficacy or if the two control methods may be synergistic. This multi-disciplinary project, which is widely supported by stakeholder groups in the West, proposes non-pesticidal, environmentally sound tactics. The goals of this 3-year field project are to evaluate the potentially synergistic effects of combining targeted sheep grazing and biological control to suppress spotted knapweed and to determine the potential effects of targeted sheep grazing on biological control insect presence and activity. Objectives include comparing the effects of biological control vs. biological control + sheep grazing at 2 different timings on: 1) the number of biological control insects present; 2) the occurrence of insect activity on buds and roots; and 3) the number of viable spotted knapweed seeds present per plant; and 4) extending results to appropriate groups and individuals. Plots will be treated with biological control only or biological control + sheep grazing in July and biological control + sheep grazing in August. Knapweed cover and density along with biological control agent populations will be monitored pre and post-grazing and at senescence. Results of this study will demonstrate the potential benefits or pitfalls of participating in integrated weed management techniques to land managers. Results will be disseminated to ranchers, livestock producers, and land managers through professional meetings, field tours, short courses, and Extension programs to facilitate the control and prevention of spotted knapweed on rangelands.
Project objectives from proposal:
The following objectives are for the complete project including all treatments and data collection to provide clear vision of the project as an entire package.
Objective 1: Compare the effects of biological control + sheep grazing in July (Treatment 1) vs. biological control + sheep grazing in August to biological control alone (Control) on the number of adult biological control insects present: 1) immediately following the sheep grazing period in July and August), and 2) at spotted knapweed senescence (September).
Objective 2: Compare the effects of biological control + sheep grazing in July (Treatment 1) vs. biological control + sheep grazing in August (Treatment 2) to biological control alone (Control) on the occurrence of pupae and larvae in buds/flower heads and roots at spotted knapweed senescence.
Objective 3: Compare the effects of biological control + sheep grazing in July (Treatment 1) vs. biological control + sheep grazing in August (Treatment 2) to biological control alone (Control) on the number of viable spotted knapweed seeds present per plant at spotted knapweed senescence.
Objective 4: Present research results to interested groups and individuals through national, regional, and local professional meetings; field days; and working group meetings. Produce research results for journal publication, popular press articles and distribution via the world wide web.