Design, Testing and Construction Education of a Post and Wire Support Structure for Insect Exclusion Netting on Field Grown Berries

Progress report for FNE20-963

Project Type: Farmer
Funds awarded in 2020: $15,000.00
Projected End Date: 02/28/2022
Grant Recipient: The Berry Patch of Stone WAll Hill Farm, LLC
Region: Northeast
State: New York
Project Leader:
Dale Ila Riggs
The Berry Patch of Stone Wall Hill Farm, LLC
Expand All

Project Information


Berry growers in the Northeast continue to battle Spotted Wing Drosophila (SWD), an invasive pest that has permanently altered production systems for berry growers.  A previous SARE Farmer Grant that I received demonstrated that exclusion netting is a highly successful method for managing this pest.  As growers come to the realization that SWD is here to stay, more growers are interested in using exclusion netting.  A major stumbling block for acceptance of this technique is the lack of any commercial companies providing support structures and the lack of a tested design and plans for growers to construct their own structures.  In this project we want to build and test an engineered system that can be replicated by any farmer willing to invest in common post and wire construction components.  I want to create professional quality construction plans, that include a list of materials, that growers will be able to access through multiple channels, to create their own support structure for exclusion netting.  Moreover, I want to teach growers, mainly through hands-on construction workshops and through YouTube videos, how to build a system for their own farm. Lastly, I intend to submit the plans developed in this project to NRCS to start the approval process for cost-sharing assistance for exclusion netting systems.

Project Objectives:

This project seeks to :

  1. Test two versions (wood post and cable and metal post and cable) of a newly available commercial support structure for insect exclusion netting, made from materials that growers can readily buy through building supply or farm supply companies or through the company that is now offering the structures.
  2. Teach growers how to construct their own support structures through on-farm construction field days and YouTube videos.
  3. Create a bill of materials and time budget for covering a half acre planting so growers can price out materials and determine the investment needed to build their own structure.
  4. Create professionally drawn plans that can be submitted to NRCS to start the process of adding exclusion netting systems to the list of approved practices for EQIP cost share programs.

SWD has forever changed berry production throughout the world.  In the Northeast, many small-scale berry growers have torn out plantings of fall raspberries and blueberries because they don’t want to spray every five to seven days to manage this pest.  My previous SARE Farmer Grant clearly demonstrated that 80 gram exclusion netting, manufactured by Tek-Knit Industries in Quebec is highly effective as a management method.  In my work, I adapted an existing bird netting support structure, made from old high tunnel hoops, to support the netting.  I have now successfully worked with this prototype for six years.  But it is a prototype that I created with materials that I had on hand.  It was not intended to be a final design for other commercial growers to use as a support structure. 

The problem is that most growers, especially if they are not growers used to using tunnels for season extension, are unfamiliar with using a hoop system for a support structure or do not feel that a hoop structure fits into their production and marketing system.  The hoop system has inherent liability problems for people that want to use it for Pick-your-own marketing, and since the hoops are not made in custom widths for lining up in blueberry rows, the system is not friendly for equipment used for maintenance during the growing season.  I have tried to get different greenhouse manufacturing companies interested in designing and manufacturing a structure, to no avail.  Interest in using exclusion netting is growing but the lack of a tested set of engineered plans for building a support structure from materials that growers can easily access is hindering adoption of this highly effective system. 

To start to address this problem, in 2018, as a test and demonstration, I constructed 2 rows of a post and wire system that I integrated into my existing hoop support system.  In an effort to keep it simple, inexpensive, and made of materials that everyone can access, I used construction quality PVC pipe and nylon high tensile wire that I had on hand.  Working informally with Chris Callahan, the Extension Ag Engineer for the University of Vermont, Chris determined what size pipe would be necessary to support the weight of rain saturated netting, and suggested fastening systems for the wire supports.  The system was workable, improving the ability to use equipment between rows, and having a continuously high ceiling in that part of the planting improved the atmosphere and reduced liability issues for pick your own customers.  However, this small demonstration also highlighted unacceptable deficiencies of this approach.   While the PVC pipe worked great for the support structure in the second (interior) row, it is not strong enough to use in the first (outer) row.  The wind resistance of the netting blowing against the supports pushed them inward so they were no longer straight.  The position of the wire that ran through PVC end caps on the top of the posts needs to be changed, and a heavier duty wire anchoring system, perhaps using earth anchors, needs to be used to ensure that the wire stays taught and does not sag.  Cross wires need to be added to the system (we just used wires lengthwise) to avoid sagging of the netting between rows.  Lastly, while the PVC pipe appears to be very smooth to avoid abrasion issues, I found that was not the case, and some holes formed in the netting due to abrasion from the netting moving back and forth across the PVC end caps.  Netting on the hoop support structure has never had these issues.

My solution is to work with Chris to design and test an engineered system that uses wooden posts for the perimeter footprint of the planting, PVC pipe for the interior supports, integrate cross wires into the structure, and create a heavier duty anchoring system.  Most importantly, we want to teach other growers, through hands-on construction field days and by creating YouTube videos, how to construct similar systems from materials that are readily available from any building materials supplier, so they can build their own support structures.

Additionally, NRCS has expressed interest in cost sharing for exclusion netting systems but cannot proceed on getting practice approval without a set of engineered plans for growers to follow and for staff to approve.  I want to use the plans developed in this project to try to start the approval process with NRCS.

Since this project was awarded funding, I found a commercial company - GinTec Shade Technologies of Ontario Canada that wanted to cooperate on this project.  They already make shade support structures for ginseng growers and are interested in making their structures usable for berry growers that want to move to using insect exclusion netting.  They offer support systems using wood posts and airline cable as well as metal posts and airline cables.  In speaking with Chris Callahan, my technical advisor, we felt it was prudent and more time effective to test the Gintec structures rather than start entirely from scratch.  Their systems include all the features that we wanted to include (a heavy duty anchoring system and cross wires) and they are engineered to withstand 80 mph winds - an important feature for possible approval by NRCS.


Click linked name(s) to expand
  • Christopher Callahan - Technical Advisor
  • Laura Griffen McDermott
  • Gregory Loeb


Materials and methods:

Working with Gintec Shade Structures, we purchased enough materials to construct a permanent support structure over our half acre commercial planting of blueberries.  We purchased supplies to use wood posts and cable on 40% of the planting and metal posts and cables on 60% of the planting.  After my proposal was written and approved Tek-Knit Industries introduced their new 85 gram netting.  It is a netting that I played an integral part in designing and encouraging them to produce.  It is designed to reduce the likelihood of long tears in the netting that may happen when abrasion of branches or some other event causes small holes to form and are then expanded by wind events.  Another innovation that I played a part in was the introduction of zippered panels. Panels of sewn netting with zippers on each side of the netting were purchased from Tek-Knit Industries of Montreal, Quebec.  The zippers were sewn into the netting by Gintec Shade Structures.  This negated the need for my past system of joining panels using a wiggle wire system attached to greenhouse purlins (straight pipes) to join panels.  That system has worked extremely well for us but Tek-Knit decided to experiment with zippered panels to make installation of netting that much easier.  The zippered panels are also cheaper for growers than purchasing greenhouse purlins at $1.00 per linear foot plus wire lock channel and wiggle wire.

In late May, Chris and I worked together to lay out and flag spots for each wooden post and metal post that would be installed. That first required us to square each corner through triangulation, and then measure down the length of the rows and across rows to flag each individual spot for post installation. To make the process more efficient, we used pre-measured pipes to ensure that we were following the same dimensions throughout the planting.

Holes for the wooden posts were made using rented single person and two person augers. Because of rocks in our soil, the augers were problematic, difficult, and dangerous to use. We then rented a “Ground Hog” hydraulically operated auger which was much safer and more efficient to use. After spending two days fighting with single person and two person augers to try to make holes for 36 wooden posts, we installed over 100 earth anchors in one afternoon with the “Ground Hog”. A special adapter had to be made for the augers that would fit on the hexagonal shaft on the auger and over the metal loop on the earth anchor but a local machine shop was able to make one for us out of heavy duty steel.

Wooden posts and metal posts were distributed to their respective locations throughout the planting. The stainless steel airline cable that was supplied by Gintec was run down the length of each set of posts, posts were set in place without yet working to get them level and cables were hand tightened temporarily. The same process was used to then run the crossways cables. Cables were attached on one end with a “dead man” fastener, and on the other end with a two bolt cable clamp. After all cables were set in place, we then used come-alongs and cable winches (provided by Gintec) to tighten each cable from the end that had the cable clamp. Each post was individually leveled in two directions and the cable winches were used to tighten the cable. The person on the deadman end of the cable would say when the earth anchor on that end started to move up, indicating it was time to stop winching the cable. The cable winches provided by Gintec were much easier and safer to use than the come-alongs obtained at hardware and tractor supply stores. Once the cables were tight, they were anchored in place with wire clamps placed on both sides of each wooden post. On the metal posts, the cables were anchored in place with J-clamps provided by Gintec.

We had wanted to have a construction field day during the actual installation of the posts but due to Covid-19 restrictions and lock-downs, we were unable to hold such an event. I may try to offer another event in April or May of this year when it is time to go through the planting and re-plumbs posts and/or cables that have loosened, but at this time, we are not sure if Covid restrictions will be loosened enough to do so.

Sewn panels of 85 gram netting from Tek-Knit were installed in two sessions. Sewn panels were numbered by Gintec (who did the industrial sewing) so that the right pieces would be joined together. Six panels were used to cover our half acre planting. The netting was pulled from one end to the other via rope. One person fed the netting from a suspended roll of netting and up over the first cable. Rope was tied to the end of the roll, thrown up over each cross cable and pulled the length of the planting. After putting up the first panel of netting, we fabricated a T out of PVC pipe that we used to help keep the netting above the cables as we pulled with the rope. It reduced the amount of friction of the netting on the cable and made the netting much easier to pull. Netting was fastened to the lengthwise cables with hog rings supplied by Gintec. Initially we just installed 2 hog rings per 15 foot section to hold the netting in place. Pieces of netting were then connected using the zippers sewn onto the edges of the panels. We had a few sections where the zippers were a bit difficult to pull but we were able to get all sections zipped together to cover the planting. Upon dismantling in the fall, I discovered that there were areas where the netting was also in the zipper channel, similar to a jacket zipper being difficult to pull when the jacket flap is entangled with the zipper pull. I believe this was the reason for some areas being difficult to zipper together.

We had intended to bury the ends of the netting under soil at the two ends, but we did not stretch the netting tight enough to provide enough extra netting at the ends to do that. We used the same system that we have used for the last 5 years – a 1” x 6” hemlock board with wire lock channel attached. We fastened the baseboards to the shafts of the earth anchors with pipe straps. We then used wiggle wire to attach the netting at the ends. We use 2 layers of strips of old greenhouse plastic between the netting and the wiggle wire to protect the netting from abrasion. We used a continuous strip of sand to bury the netting along the long edges of the planting. We re-inserted our vestibule entry that we have used for the last 6 years to finish securing the planting.  The vestibule is a key feature of my exclusion netting systems.  It's a double door entryway so that people unzip the outer doorway, enter the vestibule, close up door number 1, and then unzip door number 2 to enter the planting, zipping up door number 2 upon entry to the planting.  It reduces the human error aspect of accidentally allowing SWD to enter because a door is not closed completely, or may be blown open by the wind.  We had planned to make a larger vestibule for this year but ran out of time.  That is part of the plans for 2021.

We finished securing the netting on the planting on June 30th, 21 days after the first SWD adult was found in traps in a near by hedgerow at The Berry Patch and seven days before our first harvest. We harvested berries for commercial sale until September 3rd. During that time, 225 berries per week were harvested (25 berries from each of nine zones) and sent to Greg Loeb’s lab at Cornell Agri-Tech to determine larval infestation. No fruit infestation were found until the very last sample was collected on August 31st, when two larvae were detected from 225 berries. That results in an infestation rate of less than 1/10th of one percent over the season.

During each installation event, video and/or photographs were taken of all activities and will be edited at a later date to create You-Tube videos of each aspect of construction and installation. 

A twilight meeting was held on October 14 to discuss the entire project, share lessons learned from the new design, and discuss economics of the new design.

I have started initial discussions with NRCS regarding how to initiate the process to obtain approval for cost-sharing assistance for exclusion netting systems for commercial farms.  Based on the previous work that I have done with exclusion netting and previous conversations with NRCS they have included insect exclusion netting as an allowed expense in pest management systems but they have not included support structures for the netting.  They also have an unrealistically low cost for the exclusion netting in their practices so I have started working to document the actual costs of the netting, including the improvements with the 85 gram netting and zippered panels.

Participation Summary
2 Farmers participating in research

Education & Outreach Activities and Participation Summary

20 Consultations
1 On-farm demonstrations
1 Online trainings
1 Published press articles, newsletters
9 Webinars / talks / presentations
1 Workshop field days

Participation Summary:

50 Farmers
54 Number of agricultural educator or service providers reached through education and outreach activities
Education/outreach description:

I continue to get individual calls from growers that are interested in using exclusion netting for SWD management and I do individual consultations with them.  

We held an on-farm field day on October 14th at The Berry Patch.  This was attended by  growers and Extension personnel in person as well as live streamed to growers and service providers throughout New England via Zoom.  We demonstrated the components, supplies and tools used to construct the structure and led a tour through the planting, allowing growers to see each component up close and how the entire structure was put together.

Chris and Vern Grubinger held a SWD Management webinar on July 29, 2020 which featured this project as well as other support structures put up by growers, many of whom I have consulted with prior to building their structures.  It is available for viewing as slides or the whole webinar on the YouTube channel for UVM Extension's Horticultural Team.

Chris presented "Designing exclusion netting support systems that provide long term control of SWD and maximum utility for berry farmers" to the Northeast Tree Fruit IPM meeting on October 19, 2020.

Laura McDermott has given at least 6 presentations about the netting system at Master Gardener trainings in New York State.

Chris is giving a virtual presentation at the NY Produce Expo on January 15, 2021 and I am going to try to be in attendance to assist with any questions that may arise from that presentation.

Dale-Ila had Spectrum News come to The Berry Patch in late July and do a TV news article about the project.  It can be viewed here:

Laura discussed it with several different growers in her Extension work and through her "Berry Office Hours", held remotely during the summer of 2020.

Chris and I have consulted with Anna Wallingford and Jeremy Delisle from UNH Extension  about rolling out a program in NH that will offer some cost sharing to growers through a NRCS Conservation Innovation Grant to assist growers with modifying existing support structures or building support structures to use exclusion netting.  When Covid practices allow, they will be visiting The Berry Patch to view the structure in person and we will provide more consultation as their project progresses.  I have also offered to visit some of the proposed sites in New Hampshire to assist them with their project.

I have had several conversations with state level NRCS staff in NYS educating them about the need and utility of exclusion netting systems.  Based on conversations that I first initiated 5 years ago, they have added exclusion netting to their list of approved practices for pest management.  Unfortunately, the rate included is not high enough, but I am now working on getting them documentation to get those rates raised.

I am also on the possible speaker list for the 2022 Mid-Atlantic Fruit and Vegetable Meetings that will be held in Hershey PA, specifically to discuss this project.


Learning Outcomes

10 Farmers reported changes in knowledge, attitudes, skills and/or awareness as a result of their participation
Key areas in which farmers reported changes in knowledge, attitude, skills and/or awareness:

I personally learned a great deal about the construction process for building a structure that is specifically designed for exclusion netting.  At least two growers that attended the field day have contacted the manufacturers to get quotes for constructing a system and one grower who visited The Berry Patch while construction was occurring is planning to construct a support structure.  

Another grower that attended the field day said that she got at least three great ideas on how to make her own support structure better and to be more efficient in how she deploys the netting in the spring and takes down the netting in the fall.

I continue to get calls from growers interested in using exclusion netting and I am now able to pass on advice from this year regarding what type of materials to use and the advantages and disadvantages of using metal vs wood supports.

Project Outcomes

9 Farmers changed or adopted a practice
2 Grants applied for that built upon this project
2 Grants received that built upon this project
$50,000.00 Dollar amount of grants received that built upon this project
1 New working collaboration
Project outcomes:

This project has been very rewarding to work on in many ways.  It's been really great to see the cooperation and true teamwork that this project has brought about.  The team is comprised of those of us at The Berry Patch, UVM Extension, Cornell Cooperative Extension, and Cornell Agri-Tech.  Growers, Extension staff, and researchers working as a true team to bring this project to fruition to help the industry fight this devastating pest. This improved support structure made it much easier to be able to offer pick your own blueberries in the year that we really needed to expand our marketing channels, due to Covid restrictions and the subsequent loss of other markets.  The customers that came to our farm to do Pick Your Own blueberries were absolutely thrilled with the whole exclusion netting system - from the aspect of us not needing to spray for this invasive insect to the very calming, pleasant environment that exists under the netting.  Almost all Pick Your Own growers that I have talked with have expressed extreme pessimism about an exclusion system working for Pick Your Own operations.  My experience was the exact opposite.  I did not receive one negative comment from Pick Your Own customers and every single one talked about it being the best pick your own experience they had ever had.

Assessment of Project Approach and Areas of Further Study:

The project is not yet complete, we still have to create the YouTube videos to teach growers how to build a structure on their own.  But I think one of the keys to the success so far has been the teamwork aspect of all parts of the ag community working together to make this project happen for the benefit of the industry.  The great response to the project by the non-farm public has also been great to see.

My main question at this point regards the overall design of the structure and if it is over-built.  Reducing the number of posts in the planting would decrease the cost, but would that decrease in cost be worth the additional risk of a possible failure in the structure?  The structure is designed to withstand 80 mph winds.  We have experienced 60 mph winds.  Would a "lite" version of the structure stand up to that?  We'll never really know.  We did experience an accumulating hail event in the fall after harvest was over, but before our field day.  Even though hail accumulated up to 8 inches deep on parts of the netting, both the netting held up and the structure held up.  Paraphrasing Chris, with his engineer's training, the problem with trying to design a lighter, cheaper option is that you don't know if it's too late until it's too late and you've had a structure failure.

What I do know is that after using exclusion netting for SWD control for seven years, it is the most effective answer for SWD and I believe that this system holds promise for other insect problems in other crops.  Growing under netting, I have obtained unbelievable yields, yields equivalent to or exceeding yields in Oregon and Washington, the highest yields in the country.  The quality of the berries, and the premium price I can get for them because they are no-spray berries has given me the numbers to show that the entire system can be paid off in less than one year.  

We started our farm from a worn out old corn field with no improvements.   Twenty years later I own 245 acres, have 5 greenhouses, a full complement of farm equipment, and zero debt.  I can retire without selling my farm for retirement income.  I was able to pay off my farm mortgage 5 years early, largely because of the income that I get off half an acre of no-spray blueberries that are protected from a devastating insect by using exclusion netting.  Consumers love the system and the fact that they can get no-spray berries.  It's another example of how protected agriculture is the way of the future, particularly for small scale growers.  It can provide a decent living for growers anywhere in the country who are innovative, pay attention to detail, and keep consumer trends in the forefront of their marketing, as long as they are willing to make the investment.  When that investment can be repaid in three years or less, (less than one year in our case), there is no reason not to make the investment.  

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.