Integrating Biological Control with Targeted Sheep Grazing to Suppress Spotted Knapweed

Project Overview

SW09-068
Project Type: Research and Education
Funds awarded in 2009: $49,865.00
Projected End Date: 12/31/2012
Region: Western
State: Montana
Principal Investigator:
Rachel Frost
Montana State University
Co-Investigators:
Jeff Mosley
Montana State University

Annual Reports

Commodities

  • Animals: sheep

Practices

  • Pest Management: biological control, integrated pest management

    Abstract:

    This replicated field experiment was conducted on foothill rangeland in northwestern Montana. We evaluated the effects of combining targeted sheep grazing and bio-control insects to suppress an invasive plant, spotted knapweed (Centaurea stoebe). Populations of the three bio-control insects we studied (Larinus spp., Cyphocleonus achates and Agapeta zoegana) were not harmed by targeted sheep grazing applied in either July or August. When integrated together, targeted sheep grazing and bio-control insects provided greater control of spotted knapweed than bio-control insects alone. Targeted sheep grazing was effective when applied in either July or August, but spotted knapweed reproduction was suppressed best when targeted sheep grazing was applied in mid- to late-July, when spotted knapweed was in the late bud–early flower stage. Project results were disseminated to diverse audiences via seminars, field days and scientific conferences.

    Project objectives:

    Objective 1: Compare the effects of bio-control insects + targeted sheep grazing in July (Treatment 1) vs. bio-control insects + targeted sheep grazing in August (Treatment 2) vs. bio-control insects alone (Control) on the abundance of bio-control insects.

    Objective 2: Compare the effects of bio-control insects + sheep grazing in July (Treatment 1) vs. bio-control insects + targeted sheep grazing in August (Treatment 2) vs. bio-control insects alone (Control) on plant community fitness.

    Objective 3: Compare the effects of bio-control insects + targeted sheep grazing in July (Treatment 1) vs. bio-control insects + targeted sheep grazing in August (Treatment 2) vs. bio-control insects alone (Control) on spotted knapweed reproduction.

    Objective 4: Present research results to interested groups and individuals through national, regional and local professional meetings; field days; seminars; the worldwide web; and a research journal article.

    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.