Evaluation of Alfalfa Weevil (Coleoptera Curculionidae) Densities, Weed Abundance, and Regrowth Characteristics of Alfalfa Grazed by Sheep.

Project Overview

Project Type: Research and Education
Funds awarded in 2007: $96,817.00
Projected End Date: 12/31/2010
Region: Western
State: Montana
Principal Investigator:
Dr. Hayes Goosey
Montana State University

Annual Reports


  • Agronomic: peanuts, grass (misc. perennial), hay
  • Animals: sheep


  • Animal Production: parasite control, preventive practices, range improvement, grazing - rotational, feed/forage
  • Education and Training: extension, farmer to farmer, networking
  • Farm Business Management: budgets/cost and returns, feasibility study, agricultural finance
  • Pest Management: biological control, economic threshold, field monitoring/scouting, physical control


    Alfalfa is the foremost forage crop in many inter-mountain states. Two biological stressors,insects and weeds, combined with poor field management are primarily responsible for reduced production. Sheep grazing is emerging as a legitimate IPM tactic; however there is no published literature using degree days to implement grazing systems. Research was conducted to determine minimum and maximum degree day values necessary to utilize sheep grazing to manage spring alfalfa weevil populations. As a result, a degree day predictive model was developed to improve the effectiveness of the grazing system.

    Project objectives:

    This research was conducted at four sites in Montana. Three sites were located on stakeholder properties using stakeholder livestock to implement grazing treatments. One site was located on Montana Agricultural Experiment Station (MAES) land using MSU livestock. Based on previous work conducted by the PI, study site size varied between 100 and 350 hectares. This was a replicated research project conducted on a commercial scale, not small plot.

    Treatments are:

    1) fall/winter grazing (i.e., grazing to 0 alfalfa weevil degree days),

    2) winter/spring grazing to 25 alfalfa weevil degree days,

    3) winter/spring grazing to 50 alfalfa weevil degree days,

    4) winter/spring grazing to 75 alfalfa weevil degree days,

    5) winter/spring grazing to 100 alfalfa weevil degree days,

    6) winter/spring grazing to 125 alfalfa weevil degree days,

    7) no input control.

    Fall grazing (treatments 1 and 7) was conducted at three sites located on both MAES and stakeholder properties. Spring grazing (treatments 2-7) was conducted at one site on stakeholder property.


    1) Compare various intensities (0-125 alfalfa weevil degree days) of sheep grazing (fall and spring) and a no-input control in a multi-farm study on:

    a) alfalfa weevil larval numbers (Goosey, Tharp, Blodgett) and;
    b) alfalfa stem heights, yield and nutritive characteristics (Goosey, Tharp, Cash).

    2) Develop a specific fall and/or spring sheep grazing time-table, based on the AW degree day model, to maximize alfalfa weevil mortality (Goosey, Tharp, Lehfeldt, Baucus, Hatfield, Kott, Blodgett).

    3) Develop an economic model to evaluate long-term cost-benefits of sheep grazing and insecticides in alfalfa production (Goosey, Griffith).

    4) Develop and conduct large, multi-farm demonstrations. Communicate results to producers, students, scientist, and the public on the advantages of incorporating prescriptive sheep grazing into alfalfa production systems (Goosey, Tharp, Cash, Blodgett, Hatfield, Kott, Baucus, Lehfeldt).

    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.