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

2008 Annual Report for SW07-013

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

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


Traditional alfalfa weevil management relies heavily on the use of insecticides that target alfalfa weevil larvae. Insecticides lock producers into applications during years of high crop damage or high hay values.

Research conducted at Montana State University demonstrated that prescriptive sheep grazing can reduce alfalfa weevil populations up to 70%, prior to the growing season, without negatively impacting the quality or quantity hay. This represents a new paradigm in pest management by using strategic sheep grazing to prevent high alfalfa weevil populations and subsequent damage the growing season after grazing cessation.

Objectives/Performance Targets

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

alfalfa weevil larval numbers

alfalfa yield and nutritive characteristics

total biomass including alfalfa aftermath and broadleaf and grass weed species

change in soil in soil bulk density

Objective A will provide the PI and cooperators with the necessary data and knowledge to accurately and reliably address and implement the results of this and other relevant MSU research onto commercial farms and ranches. Can objective 1 be met within the given timetable? YES. Responses to grazing systems are not always long term; rather relevant to the grazing system and response variables as a whole. Changes in the response variables (a-d) have been documented, by the PI and others, under different grazing systems with similar timetables. If the proposed grazing will have positive/negative effects on these response variables, measuring these impacts is more than feasible within the given timetable. Additionally, this research will become part of an existing research/extension program aimed with a long term commitment to integrating sheep into farming systems. Preliminary research on these objectives has already been completed and published by the PI and additional research funds will be sought for years to come. Successful implementation of objectives 2-4 rely solely on accurate and reliable data derived from Objective A.

B) Develop a specific fall and/or spring sheep grazing timetable, based on the alfalfa weevil degree day model, to maximize alfalfa weevil mortality.

Objective B is a desired outcome resulting from both objective 1 and previous research conducted by the PI. Producer input identified this objective as a critical component necessary to teach producers how to implement this grazing system. It is necessary that the PIs develop a grazing protocol which can easily and reliably adopted by alfalfa and sheep producers. Objective B incorporates scientists, extension personal, and producers. Incorporation of the alfalfa weevil degree day development with the grazing protocol will transform these results into a user friendly approach requiring minimal producer time commitments thus increasing acceptance. Implementation of objective B relies completely on addressing objective A. Once the necessary research is completed, addressing objective B will be completed within the stated timetable.

C) Develop an economic model to evaluate long-term cost-benefits of sheep grazing and insecticides in alfalfa production.

Development of a user friendly and readily accessible economic model, in the form of an excel spreadsheet, will increase producer acceptance. This economic model would be published for ‘free use’ online via the MSU web page. Farming and ranching are a business with a bottom line of profit. The economic model will be one additional piece of information to report to producers who are concerned about input costs and net return associated with sustainable practices. Objective C will include PI participation and a MSU agricultural economist.

D) Develop and conduct large, multi-farm demonstrations. Communicate results to producers, students, scientists, and the public on the advantages of incorporating prescriptive sheep grazing into alfalfa production systems.

Objective D includes scientists, educators, extension personal, and producers. Research sites on commercial scale operations will double as demonstration sites to increase producer acceptance and awareness. After research is completed and a grazing protocol is developed and accepted by both scientific and producer based personal intimately involved in the Objectives A and B, it will become the PIs top priority to disseminate the results to interested persons and create additional interest. Objective D will be reached through developing an extensive and well-rounded outreach/extension program starting locally, moving statewide, and then to the national level.


Field work for the 2007-2008 season has been completed. The project work went smoothly with no major problems and preliminary analysis of the first year’s data looks very good. For the 2008-2009 season, four fall grazing and one spring grazing sites have been established on the same stakeholder property. Data collection will begin, according to degree-day accumulations at each site, in the spring of 2009. Field work will be completed approximately July 1, 2009. The formatting for an Excel-based, interactive economic analyzer has been begun and once field work is completed, statistical analyses will be used to complete the program, which is aimed at producer target audiences.

Impacts and Contributions/Outcomes

Currently, impacts and contributions for producers are not yet realized because we have just completed the first year and have yet to try to implement this grazing system in the agricultural community. The only change in agricultural production I have accomplished thus far with the proposed grazing system is to convince, based on 2008 results, a stakeholder involved with the fall grazing portion of the research to implement spring grazing for management of alfalfa weevil. This change will be implemented on 200 hectares of alfalfa-producing ground.

I have presented the objectives of the research at both the Montana Woolgrowers Association’s 124th annual convention and the Montana Sheep Advisory Committee board meeting during fall/winter of 2007. These meetings are attended by influential sheep producers and leaders of Montana Sheep Industry. Total attendance at both meetings was approximately 150 individuals. I will again present updated information to the Montana Woolgrowers Association at their 125th annual convention this coming December 2008 in Billings, MT.

As a final note, I decided to pursue my Ph.D and am using this Western SARE-funded research as my graduate project. I presented my research objectives and Western SARE funding source this past October 2008 for a departmental seminar, here on the MSU campus, as a component of my Ph.D. program.


Duane Griffith

Associate Proffessor-Ag. Extension Economics
Montana State University
210 B Linfield Hall
Bozeman, MT 59717
Office Phone: 4069942580
John Baucus

Seiben Livestock
Box 1683
Helena, MT 59624
Office Phone: 4064589468
Patrick Hatfield

Montana State University
119 Linfield Hall
Bozeman, MT 59717-2900
Office Phone: 4069947952
Website: http://animalrange.montana.edu/faculty/faculty-hatfield.htm
Sue Blodgett

Department Head
South Dakota State University
219 Ag. Hall
Brookings, SD 57007
Bob Lehfeldt

Lehfeldt Rambouillet
Box 175
Lavina, MT 59046
Office Phone: 4066362731
Rodney Kott

Professor-Sheep Extension Specalist
Montana State Universtiy
119 Linfield Hall
Bozeman, MT 59717-2900
Office Phone: 4069945602
Website: http://animalrangeextension.montana.edu/sheep/sheep.htm
Dennis Cash

Associate Professor
Montana State University
119 Linfield Hall
Bozeman, MT 59717-2900
Office Phone: 4069945688
Website: http://animalrangeextension.montana.edu/forage/forage.htm
Cecil Tharp

Pesticide Education Specalist
Montana State University
P.O. Box 172900
119 Linfield Hall
Bozeman, MT 59717-2900
Office Phone: 4069945067