Natural Fly Control on Rotational Grazing Silvopastures

Progress report for FNC21-1281

Project Type: Farmer/Rancher
Funds awarded in 2021: $5,866.00
Projected End Date: 01/31/2023
Grant Recipient: Harmony Hills Farm
Region: North Central
State: Missouri
Project Coordinator:
Brian Keeter
Harmony Hills Farm
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Project Information

Description of operation:

Harmony Hills Farm is a 43 acre farm approximately 1 hour west of St. Louis, MO. We purchased this farm in 2019 and are a team of two farmers who live here and are working to build a multispecies silvopasture grazing system. We started grazing South Poll cattle and added Katahdin sheep in 2021. We use portable electric fencing and move the animals frequently. Depending on many factors including weather, forage available, and time of the year, the animals are rotated between twice a day and weekly. We are working to convert this property to silvopasture by planting native trees in open pasture areas and selectively removing trees from an overgrown and previously unmanaged woodland. We experienced extreme fly pressure on our cattle herd and the only remedies that we were able to locate included pesticides which we were unwilling to use on our property. One of the goals that we are working on with our local NRCS office is increasing the dung beetle population on our farm and so we sought a non-chemical alternative to fly control.


Fly pressure is responsible for millions of dollars of loss in the cattle industry through stress, blood loss, decreased grazing efficacy, reduced weight gains, and diminished milk production in mother cows.   We would like to demonstrate an easy, low labor, and low cost method of controlling those flies.  Reduced fly pressure will allow us to have healthier animals and by using lumber from the property we will increase the acres of grazable land allowing us to increase our herd size in future seasons.   

Project Objectives:
  1. Identify the appropriate number of tree swallow houses to that will be needed to maintain a healthy population of tree swallows and minimum number of flies on the farm.
  2. Harvest red cedar lumber on the farm to expand our available pasture land. The harvested lumber will provide raw material to construct tree swallow houses to be used on the farm and sold at local farmers’ market and through our website to generate an extra income source.
  3. Evaluate health of cattle utilizing tree swallows as fly control method 
  4. Share findings through organizing an on farm field day, website/social media, instructional videos


Materials and methods:

The birdhouse design that we will be using was created by Cornell University as part of a study on Tree Swallows that they conducted in 2003.  Please see the attached pdf of their design that we will be following.  

nest box design Cornell oct 2009 (1)

Each of the pastures that we will be sampling from averages 10-15 acres. We will be monitoring the fly population using fly paper mounted near the cattle water trough.  Numbers will be tabulated weekly on the flies that are caught on the fly paper.  

By using red cedar from the property, we will build birdhouses that will last for many years and prevent us from having to rebuild or replace them due to wood rot.  Using lumber from the property also allows us to limit outside inputs and open up an additional pasture for future grazing.

We have planned a collaboration with Earthdance Organic Farm School to host a field day during the late summer in 2022 to demonstrate our project to local farmers and apprentices.  We will have printed material available for the participants at the field day in addition to a display board with pictures documenting the progress of the project.  We will be able to utilize this display board at local farmers markets as well.  In addition to documenting this project with pictures, we will make a video showing the completed project and how to assemble the birdhouse if someone wanted to make their own.

Update mid-project:

I have had to make a small adjustment to the Cornell birdhouse design.  The original design assumes that the lumber is purchased from a retail location and has nominal measurements which do not measure true.  We milled our cedar lumber to measure exactly 1" thick instead of the standard 3/4" thickness of a 1x4 purchased retail.  This caused our birdhouse to be off by 1/2" total and so the width of the front and back of the birdhouse were both increased 1/2" to 7" from the original planned 6.5".  

We have utilized the distance measuring tool on Google Earth to plot out exactly where each of the birdhouses will be placed in the two pastures.  We are currently finishing the construction of the birdhouses and will install them in the pastures in February 2022 before the spring migration of the tree swallows.  

We removed 21 cedar trees in October 2021 to be milled into lumber.  While removing these trees opened a nice path into the woods, it hasn’t yet provided enough open space to allow for livestock grazing.  We are working closely with our local NRCS office to seed a cover crop to serve as forage for local wildlife for the next several years while we work on continuing to open the canopy enough to allow for grazing of livestock.  As we develop our silvopasture, we are selecting several large healthy trees to remain in the space we are opening to provide shade for our livestock in the future.  By removing trees individually and not with heavy machinery, we are able to maintain the health of the trees that will remain and not disturb the current ecosystem. 

Additionally, we did some testing of the fly paper setup with our cattle in the summer of 2021 to work out any kinks in that setup prior to the research we will be conducting in the summer of 2022.  I had originally proposed that we would change the fly paper weekly and we now plan to change the paper with greater frequency.  In my tests, I found that once the fly paper was filled with black flies, they attracted small birds who would get stuck to the fly paper.  In order to prevent this from happening, we found that by changing the fly paper every 1-2 days prevented the birds from being attracted to it and getting stuck.  

Research results and discussion:

Portable sawmill set up at the farm and milled the cedar trees into lumber.
Cedar trees were cut and stacked with the grapple tool. The tree tops and limbs will be shredded and used for mulch in garden walkways this summer.

We are on track for our project as of this progress report in January 2022. We removed the cedar trees and had them milled into lumber.  We used the lumber to construct the birdhouses and are installing them into the pastures now.  We will begin monitoring fly population this spring and will track that data through the summer of 2022. 

Participation Summary
2 Farmers participating in research

Educational & Outreach Activities

Participation Summary:

Education/outreach description:

We have scheduled a field day for a group of local livestock farmers in collaboration with Lincoln University and the NRCS that is scheduled for September 20, 2022.  We will have presentations by the NRCS on soil health, a demonstration by the small ruminant specialist from Lincoln University on using the NRCS grazing stick to track forage, and a presentation by Harmony Hills Farm on the results of this SARE project.  We also plan to include a tour to show our rotational grazing system.  

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.