Extending the Market Season with High Tunnel Technology for Organic Fruit Production

2014 Annual Report for LS12-250

Project Type: Research and Education
Funds awarded in 2012: $214,948.00
Projected End Date: 12/31/2015
Region: Southern
State: Arkansas
Principal Investigator:
Dr. Curt Rom
University of Arkansas

Extending the Market Season with High Tunnel Technology for Organic Fruit Production


A series of two primary studies using high tunnel technologies and modifications to tunnels were conducted to determine how the technologies may fit into sustainable and organic fruit production systems in the south.  The two studies were using high tunnels (HT) for 1) advancing summer ripening blackberries, and 2) extending the harvest season of autumn ripening blackberries and raspberries.  Preliminary studies have indicated the potential for both.  Tunnels were modified to include A) low-tunnels within tunnels (tunnel-in-tunnel) around the fruiting plants, B) covering plants with 30% shade to reduce heat and light load to delay flowering and fruiting and improve fruiting, and C) to screen the tunnels to exclude deleterious insect pests.   The goal is to develop a tunnel production system that may compliment a field production system by extending the harvest season, expanding cropping, improving fruit quality, and be especially adaptable to sustainable and organic production systems.  

In the second year of the study, data indicate that high tunnels have the opportunity to increase overall harvest and improve marketable yield, and significantly improve cumulative harvest during the establishment period of berry production.   Spring deployed high tunnels may advance the harvest approximately 2 weeks and tunnel-in-tunnel systems can advance the crop an additional 10 to 14 days.   The high tunnels can result in reduced crop loss due to frosts if supplemental heat is added to the tunnel, and tunnels in tunnels improve this even more.  A problem with autumn bearing primocane blackberries and raspberries is flowering and fruiting in the heat of the summer season (July and August) and cropping being poor.  It was hypothesized, based on preliminary observations and other production systems, shading may delay flowering and fruiting.  However, after two years study, only minimal changes in the timing of flowering and fruiting were observed.  Additionally although yields of raspberries were increased by shading, yields of blackberries were significantly reduced by shading.   Shading cannot be recommended for blackberry but is a potential tool for delaying harvest and improving cropping of raspberries. 

Screening the high tunnel with insect netting was an effective means to reduce spotted wing drosophila damage.  Brambles in the screened high tunnel and open field had season mean totals of 8.5 and 290.8 spotted wing drosophila (SWD) flies per trap, respectively, and 1.3% and 63.3% SWD-infested harvested fruit in the high tunnel and field, respectively.  However, the screen increased air temperatures that caused deleterious spider mite and aphid outbreaks.

Three interactive decision support tools were created to help producers to estimate expected costs, revenues and net returns associated with blackberry, blueberry and raspberry production in field or high tunnel systems. Breakeven, sensitivity and risk analyses functionality is included to allow for more complete economic profitability considerations.  Expected profitability can be calculated using the producer’s own production system information and expected selling prices. 

Project information was extended to growers, extension educators, scientists and students through local and regional grower conferences and meetings, a regional scientific conference, a national growers conference, a blog, farm tour, and class room discussions and tour.  Talks were given on economics, pest management, sustainability and high tunnel production methods and modifications. The Blackberry and Raspberry Sustainability Checklist for growers is being finalized for release spring/summer 2015.

Objectives/Performance Targets

The purpose of this project is to extend the sustainable production of summer berries using HT technology to achieve earlier spring harvest of blueberries and blackberries, and to allow for an extended autumn production of new primocane blackberries and raspberries. The goal of the project is to develop an environmentally and economically sustainable organic fruit production systems combining HT production with traditional FD production and providing for further expansion of organic crop production in the southern region. 

The specific project objectives were:

  1. To develop High Tunnel (HT) production systems for season extension of organic high value fruit crops for the southern region.
  2. To develop and test pest management strategies for organic HT crop production systems adapted to the southern region.
  3. To estimate economic models and to create decision support tools that help producers to manage production systems for profitability considerations
  4. To extend the knowledge acquired through the production, pest management, and economic analyses into a multi-dimensional educational, outreach, and extension program.



The 2014 production season was the second year of full production of the two studies within this project.  Each study is presented separately.

Study 1.  Advance cropping of summer floricane blackberries with High Tunnels (HT) and Tunnel-in-Tunnel (TNT) use compared to field (FD) production.

Spring floricane blackberries (cv Natchez) in the HT produced significantly more total fruit and marketable yield, with peak harvest approximately two weeks earlier than similar plants under field conditions.  The HT reached the 50% harvest point just as FD fruit were first harvested.  The HT produced more than twice as much fruit than the FD.  Fruit were approximately 10% larger but had lower soluble solids.   Across the two seasons, HT had an average 18 day crop advance compared to the FD.  Cumulative yields in the HT were approximately 40% greater than those in the FD.

The TNT system advanced harvest an additional week compared to the HT alone and a two-year average crop advance of 25 days compared to the FD.  The TNT provided significant heat conservation on cold nights during the bloom period.  Additional pollination was needed within the TNT.  Yields, average berry size, and % marketable fruit between the TNT and HT alone were similar but greater than the FD.

Blueberries did not crop in 2014 in the HT and blueberries in the field died due to poor plant health at planting and difficulties with establishment.

An additional study on the water use and water use efficiency of HT compared to FD conditions was added to the study.  Although data are still being analyzed, it appears that the HT used more irrigation water compared to FD production systems.  However, the water use efficiency on a water per unit of fruit produced basis was similar between the HT and FD.  

Study 2.  Extend the harvest season of autumn primocane blackberries with HT, TNT, and shade treatments compared to the FD. 

Primocane fruiting blackberries (cv PrimeArk45®) grown in the HT produced 60% more fruit than the comparison FD treatment.  The cumulative yield across the first seasons of this study was more than 200% greater in the HT compared to the FD.  There was no difference in time of harvest.  However, fruit in the HT had an extended harvest period of approximately 1 week across both seasons compared to the FD before severe freezes ended production.  The TNT extended harvest an additional 2 weeks with additional freeze protection. 

Although preliminary evidence indicated shading primocane blackberries may be a strategy for delaying bloom and harvest, and this was confirmed in both the field and greenhouse studies, shading significantly reduced yields in both years of the study.  This was not true for raspberries and in fact was the opposite with shading increasing fruit yield in primocane raspberries. An additional study of the effects of shade on growth, development, physiology and fruiting of blackberry was conducted.   Further testing of shading as a strategy to manage timing and harvest of blackberries will be discontinued in the coming season. 

The raspberry portion of the study was discontinued at season-end in 2014 due to plant death induced by a combination of severe mite infestations, root rots and high temperatures inside the screened high tunnel.

Spotted wing drosophila (SWD) was first observed in 2011 in Arkansas and developed into a serious pest by 2013.  In 2014, the primocane fruiting high tunnel was screened with 25 gram mesh, 0.5 x 0.5 mm, ProtekNet insect netting in anticipation of high spotted wing drosophila (SWD) pest pressure. Screened and open field plantings resulted in season totals of 8.5 and 290.8 SWD flies per trap and season means of 1.3% and 63.3% SWD-infested harvested fruit, respectively.  The organic SWD spray program applied to only open field brambles during harvest and included 6 biweekly sprays of Entrust rotated with Pyganic from 15 July to 4 October. However, this fine mesh screen reduced airflow by over 30% which caused the temperature in the high tunnel to exceed 95?F and 100?F on 18 and 13 days, respectively, with a one day high of 105.8?F. In comparison, ambient temperatures outside exceeded 90?F on only 11 days with a one day high of 95.4?F.  These hot temperatures also resulted in decreased marketable fruit.  Only the high tunnel had deleterious outbreaks of spider mites on the raspberries from June on that eventually killed the plants and aphids on blackberry terminals in fall and spring that also reduced yield.  These mites could not be controlled by JMS Stylet Oils (too hot to apply) nor three weekly releases of 1,000 Neoseuilus californicus predatory mites. 

A new study was initiated in 2014 to study overhead misting to remediate high temperatures in the screened HT.  Micromisters were installed along the ceiling centerline purlin.  Two systems of misting were tested, a one-hour mist and a four-hour continuous mist.  Misting almost instantly reduced tunnel temperatures to ambient, external temperatures (or slightly below).   After a one-hour mist, the tunnel temperature returned to temperatures above the ambient, external temperatures within 45-60 minutes.  Likewise, during a 4 hour mist, the HT temperatures were at or below ambient, external temperatures.  HT temperatures returned to above the ambient, external within 45-60 minutes after discontinuing misting.  The misters used in the experiment resulted in wet foliage and fruit, increasing the potential for disease and fruit rots, although none was observed with the way the study was conducted in this year.  Because of these results, additional studies will be continued in 2015 by replacing the misters with foggers with significantly reduced water output.   Additionally, to control tunnel temperatures, tunnels are being fitted with roof and ceiling vents to improve air circulation

New interactive economic budgets have been developed that are unlike any previously available in the state or region. These budgets are currently being used and tested by county extension and berry producers to ensure the quality of the data and models included. These tools are currently in demand not only in Arkansas but also in Missouri and Oklahoma where they have been demonstrated and advertised. 

The user-friendly interactive decision support tools for blackberry, raspberry and blueberry encompass budgeting, economics and risk components with the ability to calculate actual and “what if” analyses in ways that berry producers could not have done before. These free tools allow berry producers, extension agents, policy makers and educators to perform and customize economic assessments of production practices before adoption into their operations. The blackberry and raspberry budgets have been released and the blueberry budget is forthcoming, mid-Spring. These resources are available on the Center for Agricultural and Rural Sustainability website, http://cars.uark.edu/ourwork/Specialty-Crop-Production-and-Marketing/fruit_budget.aspx . Our tools have been introduced to producers and educators and feedback is being used to improve the tools’ functionality and applicability.

Several presentations were made to growers, extension agents and scientist in the past year to extend information learned and experiences gained in this project.  Whole to half day high tunnel fruit workshops were offered at the 2015 AR-OK Horticulture Industry Show, an annual growers’ conference and the Missouri Organic Association 2015 annual conference. These talks included a comparison of high tunnels and open field production of brambles; high tunnel modifications to improve berry performance; Spotted wing drosophila; using interactive budgets in fruit production; and the Blackberry and Raspberry Sustainability Checklist.  Additional high tunnel fruit talks were given at the North American Raspberry and Blackberry Growers Association annual conference, Lincoln University and University of Missouri. Project posters were presented at Southern Region American Society of Horticultural Science and the North American Raspberry and Blackberry Growers Association annual conference.  These presentations can be viewed here, http://cars.uark.edu/ourwork/Specialty-Crop-Production-and-Marketing/hightunnelorganic_fi.aspx, or http://hightunnelberries.uark.edu/2015/03/02/high-tunnel-berry-presentations/.  Presentations are also available upon request.  The project blog, http://hightunnelberries.uark.edu/, has also informed growers of plant growth, production practices, project developments and information, and resources.

In the coming year there will be a significant amount of activity extending project and production information to growers. At least three short videos of key production practices are in development and will be posted to the blog. “Sustainable Blackberries and Raspberries: A self-assessment workbook for growers” is currently being published. This is a tool that growers can use to evaluate their production and farm on an annual basis. There will also be two webinars – one on the sustainability checklist and the other on high tunnel bramble production and a berry production school is in development for spring 2015.

Impacts and Contributions/Outcomes

These studies have indicated that HT alone can extend the production season of berries approximately 2 weeks on each end of the season.  The use of TNT provides additional crop advance and season extension by approximately an additional 1-2 weeks.  Additionally, the TNT has provided superior protection against crop damaging freezes.  The TNT causes the challenge of needing higher populations of pollinating insects.   The plants in the HT and TNT were larger than in the FD.  They produced increased crop due to larger plants, extended production season, and freeze protection.  Additionally fruit were larger in the HT and TNT than in the FD.  The marketable percentage of harvested fresh fruit was greater in the HT than the FD increasing the value of the production system.  Early indications from the study are that the HT system is likely not a replacement to FD production but is a compliment to advance and/or extend the berry production season. 

Screening the HT to minimize insect pests was a very effective strategy but posed new challenges in HT temperature management.  Shading did not significantly reduce HT temperatures although there is the potential for micro-misting or fogging the tunnel for evaporative cooling.  

The economic tools developed in this project may assist berry producers in making economically sound decisions that can contribute to the growth of berry production acreage in Arkansas and across the south.

As a result of the multi-dimensional outreach activities, growers, extension agents and scientists are learning about this project and gaining interest in high tunnel fruit production. Information from this study is being presented at local, regional, and national grower workshops/conferences, and at national scientific and extension meetings.  Two significant grower tools, the interactive budget and the sustainability checklist, have been developed to inform growers and help them make better decisions on their farm to improve their overall farm sustainability.  Over 200 growers and extension agents received these tools through the various presentation and conferences this past winter.  There has been an increase in emails and calls for more information on workshops and field days.


Donn Johnson

Professor, Entomology
University of Arkansas
AGRI 311
Fayetteville, AR 72701
Office Phone: 4795752501
Website: http://comp.uark.edu/~dtjohnso/
Jennie Popp

Professor, Ag Business and Economics
University of Arkansas
AGRI 217
Fayetteville, AR 72701
Office Phone: 4795752279
Elena Garcia

Professor Extension Specialist
University of Arkansas Cooperative Extension
316 PTSC
Fayetteville, AR 72701
Office Phone: 4795752790