Final report for LNC18-404
Project Information
Cucurbit crop growers in the North Central Region struggle to control cucumber beetles and the bacterial wilt pathogen they spread. The bacterium kills plants, depresses yield, and drains profits. Insecticide sprays are widely used against the cucumber beetles but damage pollinators and other beneficial insects, so their sustainability is in question. Muskmelon is highly susceptible to bacterial wilt, and organic growers often avoid planting this crop because yield losses can exceed 80%. Alternative management tactics such as biochemical lures, perimeter trap cropping, delayed planting, and crop rotation have not been reliably effective. Low tunnels covered by spunbond polypropylene fabric work well until they are removed to allow pollinator access, but then muskmelon can collapse and die from mid- to late-season wilt outbreaks. We have been testing an innovative variation on the protective tunnel theme that we call mesotunnels. Mesotunnels are more than twice as tall as low tunnels and are covered by a breathable nylon-mesh fabric that remains in place all season, with bumble bee colonies inserted underneath for pollination. In small-plot trials in Iowa in 2016 and 2017, mesotunnels increased marketable yield of organic muskmelon by an average of 450% compared to low tunnels or insecticide-only treatments – without using any insecticides. This approach therefore has promise to deliver consistently high marketable yields without the risks associated with insecticide use – a change that could open up new growing and marketing opportunities for organic cucurbit growers. Our proposed project will take the essential next steps to make mesotunnels into a workable alternative for North Central Region growers. Two years of field experiments under organic management will assess living mulches for weed control and soil quality improvement, and optimize the efficiency of purchased bumble-bee colonies for pollination under commercial-size mesotunnels (Objective 2). We will compare profitability of the mesotunnel system to current management strategies and work closely with growers to understand the factors that impact their views of the new system (Objective 2). Our intensive outreach program, mixing on-farm demonstration trials and field days in Iowa and Missouri with electronic features such as webinars and an online manual for growers, will ensure that the project’s messages reach cucurbit growers throughout the NC Region (Objective 3). Our results will have application to additional cucurbit crops that are susceptible to bacterial wilt, and for conventional producers seeking to minimize reliance on insecticides.
• 250 NC Region muskmelon growers become aware of the potential value of mesotunnels to suppress pest insects and bacterial wilt.
• 80 growers learn how to use mesotunnels on their cucurbit crops
• noo growers understand the economic tradeoffs of using mesotunnels for cucurbit production.
• 60 growers (including 30 organic growers) plan to try mesotunnel systems on their own farms within 2 years.
• 30 growers try mesotunnels in their muskmelon fields during the project period.
Bacterial wilt, caused by Erwinia tracheiphila, causes yield losses for cucumbers and muskmelon that can exceed 80%, and also decimates pumpkin, winter squash, and zucchini. Bacterial wilt-resistant cultivars of muskmelon and cucumber are nearly non-existent.Stopping cucumber beetles is currently the only effective way to combat bacterial wilt on highly susceptible crops like muskmelon, honeydew, and cucumber. Neonicotinoid insecticides are widely used against striped cucumber beetle (Acalymma vittatum) and spotted cucumber beetle (Diabrotica undecimpunctata). However, these and other pesticides weaken or kill pollinators and reduce populations of insectivorous birds. Synthetic pyrethroid insecticides are also widely used but kill natural enemies. Yield losses from bacterial wilt jeopardize growers’ sustainability. CSA customer dissatisfaction, unfulfilled contracts with cooperatives, and quality issues with wholesale clients can threaten economic viability and resilience of cucurbit growers. This problem is especially acute for organic growers because there are no consistently effective organic management strategies against bacterial wilt. With funding from NIFA Organic Transitions (2015–2018), our ISU team began evaluating an innovative protection system called “mesotunnels” to overcome disadvantages of low tunnels. Mesotunnels are covered with a tough nylon-mesh fabric that is far more durable and breathable than spunbond fabrics. Mesotunnels are also much taller (3.5 ft.) than low tunnels (1.5 ft), so there is more room for plant growth and no overheating of plants. Unlike low tunnels, mesotunnels can protect cucurbit crops for the entire growing season. Despite encouraging preliminary results, several key questions must be answered before mesotunnels can be recommended for use by growers:
- Can mesotunnels be scaled up effectively from small-plot experiments to commercial-size muskmelon plantings?
- What is the most cost-effective way to deploy purchased bumble bee colonies for pollination under full-season mesotunnels?
- Can living mulches be used to control weeds under mesotunnels while also enhancing soil health?
- Will higher and more consistent marketable yields increase profits despite the higher cost of mesotunnels?
Our 2-state (Iowa and Missouri), 2-year project will answer these questions in organic muskmelon, for which bacterial wilt is especially threatening, with an integrated program of field experiments, economic and stakeholder assessments, on-farm demonstration trials, and outreach.
Research
- In 30-ft-long mesotunnel plots of organic muskmelon, each of 2 seeding rates of teff (4 and 8 lb/A) will a) suppress weeds between rows as effectively as weed fabric and b) result in marketable yield equivalent to that of the weed-fabric treatment.
- In 150-ft-long mesotunnel plots of organic muskmelon, inserting a purchased hive of bumblebees inside mesotunnels during flowering will result in higher marketable yield than either a) opening the ends of the tunnels or b) removing the tunnel fabric for 2 weeks during bloom.
- In 150-ft-long mesotunnel plots of organic muskmelon, either a) removing mesotunnel fabric or b) opening the ends of the tunnels for 2 weeks during flowering will result in increased incidence of bacterial wilt compared to a treatment in which a bee box is inserted under the mesotunnel fabric.
Weed management with mulches in mesotunnels. At the Iowa State University Horticulture Research Station near Gilbert, Iowa, during 2020 and 2021, muskmelon (cv. Athena) seedlings were transplanted into 30-ft-long, 3-row subplots spaced at 6 ft on black plastic mulch, under full-season mesotunnels (3.5-ft-tall tunnels with ProtekNet nylon-mesh fabric supported on steel-conduit hoops). One bumblebee box was placed during bloom in each subplot for pollination. In 2020, four mulch treatments, arranged in a randomized complete block design, were applied to bare-soil strips between black plastic: 1) teff living mulch (seeded at 4 lb/A), 2) teff at 8 lb/A (both seeded at the time of transplanting the crop), 3) plastic landscape fabric and 4) bare ground (control). Rationales for using these treatments: 1) they encompass a wide range of the weed suppression tactics used by organic cucurbit-crop growers in the North Central Region; and 2) weed control under mesotunnels poses special challenges because there are no opportunities for mowing or other organic tactics during the growing season, so we sought to test tactics with potential to provide full-season weed suppression. Yield data were taken on the center row of each 3-row subplot; the number and weight of marketable fruit were recorded at harvest. Above-ground weed biomass was assessed immediately before crop harvest began.
In 2021, treatments were modified to add a component of mowing the subplot alleys. Treatments were: ) teff living mulch seeded at 4 lb/A, mowed at the start of bloom; 2) teff seeded at 4 lb/A but not mowed; 3) plastic landscape fabric; 4) bare ground, weeds mowed at start of bloom; and 5) bare ground, weeds not mowed. Rationale: because teff suppressed crop yield in 2020 without mowing but suppressed crop yield, in 2021 we tried mowing about 3 weeks after transplanting to get teff's weed-control benefits but minimize the yield drag. A mowed treatment for the weeds that arose in bare-ground treatment was added to compare with the mowed teff and the non-mowed bare-ground treatments.
Pollination strategies in mesotunnels. At the Iowa State University Horticulture Research Station near Gilbert, Iowa, during 2020 and 2021, muskmelon (cv. Athena) seedlings were transplanted into 150-ft-long, 3-row subplots on 6-ft row spacing in a randomized complete block design. Plastic landscape fabric was installed in alleys at transplanting to control weeds. All plots were covered with mesotunnels (3.5 ft tall, with nylon-mesh fabric (ProtekNet) on steel-conduit hoops) immediately after transplanting. Treatments were: 1) a bumble bee hive (Koppert Inc.) per subplot (full-season tunnels); 2) tunnel ends opened for two weeks during bloom, then replaced (open-ends treatment); and 3) ProtekNet fabric was removed for 2 weeks during bloom, then replaced (on-off-on treatment). The rationale for selecting these treatments was that we realized that some growers might not be able to purchase bees or they might be too costly, so we wanted to include lower-input-cost alternatives. Visual observations of bee activity on muskmelon flowers were made twice a day in all treatments between 8:00 and 11:00 AM on three days per week during two weeks after female flowers appeared. Disease incidence and severity were rated on the center row of each subplot and recorded weekly. Number and weight of marketable fruit data were recorded at harvest on the center row of each subplot.
Weed management with mulches in mesotunnels. RESULTS: In 2020, marketable yield for landscape fabric was about twice as high as for the other three treatments, although teff suppressed weeds almost as well as landscape fabric. In 2021, mowing teff at the start of crop flowering resulted in no significant difference in marketable yield compared to the landscape-fabric control treatment. DISCUSSION: The yield penalty from teff compared to landscape fabric was attributed to root competition with the crop for nutrients, water, and sunlight during an abnormally dry growing season. Although teff did a great job on weed suppression, its vigor and drought tolerance made it a potent competitor with the muskmelon crop. However, our 2021 results showed that mowing teff when female flowers first appeared resulted in excellent weed control but no significant yield suppression compared to landscape fabric. No such yield boost associated with mowing was found for the so-called bare-ground (actually, very weedy) control treatment. As a result, we conclude that it is possible to manage teff as a living mulch to achieve both good weed control and excellent marketable yield for muskmelon in mesotunnel systems. However, it is likely that proper timing of mowing teff in the alleys is critical; waiting beyond about 3 weeks from transplanting may incur a yield penalty and risk interference of the growing vines with the mower, whereas mowing too early may diminish weed control.
Pollination strategies in mesotunnels. RESULTS: In both 2020 and 2021, marketable yield was highest for the full-season mesotunnel treatment, intermediate for the open-ends treatment, and lowest for the on-off-on treatment. Bacterial wilt incidence was slightly higher in the on-off-on treatment than the other treatments, but its impact on yield was unclear. DISCUSSION: The consistent yield boost for the full-season treatment compared to the other treatments suggests that it has potential for organic producers. However, an economic analysis is being conducted to determine which treatment is most cost-effective.
Conclusions for Final Report:
- In Iowa, based on our 2-year study, teff appeared to have promise as a living mulch for muskmelon in mesotunnel systems. Teff out-competed weeds; and if mowed at the right time (about 3 weeks after transplanting), its competition with the muskmelon crop did not hinder yield. Living mulches can he highly beneficial for growers because they can build organic content of the soil while suppressing weed growth and thereby weed seed development. Teff is a good candidate we have found because of its vigorous growth - but it must be controlled with timely mowing. Landscape fabric provided excellent weed control with no yield drag, but requires an additional off-farm input. It can be stored and re-used, providing adequate labor and space are available.
- In both 2020 and 2021, the full-season pollination strategy, with mesotunnels remaining in place all season and bumble bee hives inserted underneath for pollination, was the most promising treatment from a marketable yield standpoint. An ongoing economic analysis is aiming at determining cropping scenarios (e.g., scale of muskmelon cultivation, number of years for which the nylon-mesh covering can be re-used, and price for purchased hives) under which the full-season pollination strategy can be advantageous for organic muskmelon growers.
Education
On-farm demonstration trials.
- Iowa. An on-farm trial was held in 2020 at Middle Way Farms, Grinnell, Iowa; grower-cooperator was Jordan Scheibel.
This project focused on the use of mesotunnels for integrated insect management in sustainable vegetable production. An on-farm trial grower-collaborator trial was established at Middle Way Farms, Grinnell, IA. The farm is owned and operated by Jordan Scheibel. The farm is a small, chemical-free, direct market vegetable farm just outside of Grinnell, Iowa, selling seasonally May through December to customers in Grinnell, Newton, and the surrounding area.
Growing season: The research focused on utilizing watermelon as a crop to test and compare ProtekNet vs. no-cover treatment. Due to inclement weather and a wet spring planting was delayed. Three week old watermelon seedlings were transplanted on raised black plastic mulch beds on 3 July 21. Treatments included a no-cover and ProtekNet. The ProtekNet netting was installed on 6 July 2020. Each treatment was 40 ft. long and there were three replications for each treatment. ProtekNet were removed on 9 August 2020 to facilitate pollination. One-time harvest was conducted on 13 October 2020.
There was no difference in marketable fruit number or weight between treatments (Table 1). Marketable fruit count ranged from 21 to 23 and weight ranged from 93.2 to 99.4 lbs. Insect damage was recorded on the fruit at the time of harvest but there were no differences between treatments. Overall, the yield from the entire study was low and this is due to the damage caused to the plants by Derecho storm which took place on 10 August 2020. Many of the plants had severed stems and were damaged by the hail that was part of the Derecho.
Air temperature data was continuously collected during the growing season using Hobo sensors (Onset Data Loggers, Bourne, MA). There were no significant differences in air temperature between treatments for the month of July (Table 2). There were significant differences in light intensity between treatments for the month of July with Protek net reducing light intensity by 25% (Table 2). We also collected grower feedback on plant vigor, difference in insect damage and pest pressure, ease of installation, management challenges, and cost associated with Protek net treatments.
Based on the feedback from Jordan, ProtekNet treatments could have provided the benefit of insect protection if the crop was planted earlier, typically beginning of June. In 2020, the crop was planted in July when major insect pests had already taken hold on other crops. Also, since the farm was not able to reinstall the ProtekNet after pollination, all treatments were exposed to the insects and other environmental factors. The major setback was the Derecho event which did not allow for a fair comparison of the treatments as the entire study was heavily impacted.
Another challenge was to manage weeds in the ProtekNet treatment. Although the farm applied straw mulch between rows, the thickness of the application was not enough to stop weeds from emerging. One of the strategies moving forward could be the use of weed fabric between rows where Protek net treatments are being installed.
In 2021, Iowa on-farm demonstration trials were held at 1) Scattergood Farm near West Branch, 2) Humble Hands Harvest Farm near Decorah, and 3) Blue Barrel Farm near Cuba City. All three trials compared production of butternut squash in three regimes: mesotunnels; low tunnels; and non-covered. Each trial had three replications (25- or 50-ft-long rows) per treatment. All three farms used ProtekNet as the mesotunnel fabric, with landscape fabric installed between rows for weed control. At Blue Barrel Farm, the mesotunnel and non-covered treatments has significantly higher marketable yield than the low-tunnel treatment. At Humble Hands Harvest Farm, the mesotunnel treatment had significantly higher yield than the non-covered treatment, and the low-tunnel treatment had significantly lower yield than the other two treatments. These results emphasize that mesotunnel systems have potential to increase yields of cucurbit crops other than muskmelon, although economics of this approach need to be compared with other organic strategies.
- Missouri. In 2020, an experiment was conducted with 'Athena' muskmelon at the Organic Farm of Lincoln University in summer 2020. The experimental design was a randomized complete block design with 2 treatments (non-covered control and mesotunnel); 3 sections; 3 blocks per section and 10 plants per block. Transplanting took place on June 12. Cucumber beetle populations were extremely low, and bacterial wilt symptoms were not evident in the field. Statistical analysis of the yield data has not been done yet. In 2021, no trials or extension events were conducted due to restrictions imposed by the COVID-19 pandemic.
Field days.
- The Iowa field day at the ISU Hort Research Station, scheduled for August 2020, was canceled due to the pandemic.
- In Missouri, a field day that was held near Jefferson City, MO, on July 12, 2020, included a grower tour of the NCR-SARE demonstration plot.
- In Iowa, a field day was held at the Iowa State University Horticulture Research Station on July 22, 2021. Attendance was 175. Gleason's PhD student, Kephas Mphande, reported to attendees on progress of his two 2021 field research experiments at the ISUHRS on organic muskmelon. These experiments were largely repeats of the SARE-funded trials in 2020, except that weed management trial treatments were broadened to include both mowed and non-mowed treatments of teff as well as bare-ground control (weeds). See Research Results for details.
Meeting presentations.
Dr Ajay Nair (ISU co-PI) presented two formal talks relating project purposes and results:
-
- PFI Annual Conference: Grower panel
Date: 01/21/2021
Number of attendees: 35
- Title: Integrated pest management in sustainable vegetable production systems
Conference: Iowa Specialty Producers Conference
Date: 01/20/2021
Number of attendees: 19
- Title: Specialty Crop Production: Grower panel
Conference: Iowa Specialty Producers Conference
Date: 01/20/2021
Number of attendees: 15
4. Cheek, M., and Eaton, T. 2021. Mesotunnels as an alternative to insecticides to control cucumber beetles in muskmelon. Poster presentation, Great Plains Growers Conference, February 12-13, 2021.
5. Gleason, M.L. 2021. Mesotunnels: exploring a new approach for organic cucurbits. PowerPoint presentation, Great Plains Growers Conference, February 12, 2021.
Mr. Mphande also submitted Iowa State two research reports (one on each field experiment), summarizing 2021 results, that are awaiting publication by the ISU Agriculture Experiment Station as part of their Farm Reports series (they have not yet been assigned URLs). These research reports are intended for grower use.
Electronic resources.
- Project website entitled "The Current Cucurbit" (https://www.cucurbit.plantpath.iastate.edu) includes blog posts, videos, and reports developed jointly for the the NCR-SARE project and the NIFA-OREI project during 2020.
- Average number of visits to website per month, January-October 2021: 90.
- BLOG POSTS:
- Gleason, M.L. "What's a mesotunnel, and what's it good for"? July 24, 2020. Blog post. (https://www.cucurbit.plantpath.iastate.edu/post/whats-mesotunnel-and-whats-it-good)
- Pethybridge, S. "Mesotunnels: next best tool for organic cucurbit growers in the Northeast U.S.?" August 14, 2020. Blog post. (https://www.cucurbit.plantpath.iastate.edu/post/mesotunnels-next-best-tool-organic-cucurbit-growers-northeastern-us)
- Gonzalez, J. "Planning for success: IPM approaches in organic cucurbit production" August 28, 2020. Blog post. (https://www.cucurbit.plantpath.iastate.edu/post/planning-success-ipm-approaches-organic-cucurbit-production)
- Chen, N., and Zhang, W. "How do we assess the economic efficiency of mesotunnels? An economist's take" September 18, 2020. (https://www.cucurbit.plantpath.iastate.edu/post/how-do-we-assess-economic-efficiency-mesotunnels-economists-take)
- Gonthier, D., and Bessin, R. "Balancing pollination and pest control in mesotunnel cucurbit systems" October 2, 2020. (https://www.cucurbit.plantpath.iastate.edu/post/balancing-pollination-and-pest-control-mesotunnel-cucurbit-systems)
- Badilla, S. "Optimizing weed control under mesotunnel systems: Iowa State's 2020 experience with acorn squash" October 16, 2020. (https://www.cucurbit.plantpath.iastate.edu/post/optimizing-weed-control-under-mesotunnel-systems-iowa-states-2020-experience-acorn-squash)
- Mphande, K. "A look at 2020 muskmelon trial results from Iowa State University (ISU)" October 30, 2020. (https://www.cucurbit.plantpath.iastate.edu/post/look-2020-muskmelon-trial-results-iowa-state-university-isu)
- Morton, L.W. "Crop diversification as a risk management strategy" November 13, 2020 (https://www.cucurbit.plantpath.iastate.edu/post/crop-diversification-risk-management-strategy)
- Gleason, M.L. "Summary of 2020 season results" Notes from OREI cucurbit mesotunnel virtual project meeting with grower Advisory Panel, October 2, 2020. (https://www.cucurbit.plantpath.iastate.edu/files/inline-files/OREI%20Annual%20Virtual%20Meeting%232%20Highlights%20final%20-%202020%20%28untraceable%20ver%29.pdf)
- Morton, L.W., Cheng, N., Diggins, K., and Gonzalez, J. "Technical report: cucurbit growers' perceptions of mesotunnel production systems" January 27, 2021. (https://www.cucurbit.plantpath.iastate.edu/files/inline-files/Growers%20perceptions%20-%202020%20final%20report.pdf)
- Nair, A., and Gleason, M.L. "Summary of the 2020 on-farm trials from Iowa: effect of ProtekNet mesotunnels on cucurbit crop production and microclimate management" (https://www.cucurbit.plantpath.iastate.edu/files/inline-files/On-farm%20trials%20Iowa%202020.pdf)
- Gleason, M.L. "Summary of the 2020 field trial results" (https://www.cucurbit.plantpath.iastate.edu/files/inline-files/OREI%203-state%20field%20trial%20summary%202020.121.pdf)Surveys
- Zhang, W., and Chen, N. 2021. "The OREI cucurbit crops project year 1 and Whole Team/Advisory Panel/Cooperating Grower survey" February 2021 (https://www.cucurbit.plantpath.iastate.edu/files/inline-files/OREI_Year_1_Survey_Report_Feb2021.pdf)
- Diggins, K., and Morton, L.W. 2021. “What are growers saying about mesotunnel systems for organic cucurbits?”Link: https://www.cucurbit.plantpath.iastate.edu/post/what-are-growers-saying-about-mesotunnel-systems-organic-cucurbits
- Cheng, N., and Zhang, W. 2021. “What do Farmers and Researchers Think About Mesotunnels and Biological Controls for Cucurbit Crops? Responses from 2020 surveys”, by Nieyan Cheng, and Dr. Wendong Zhang. Link: https://www.cucurbit.plantpath.iastate.edu/post/what-do-farmers-and-researchers-think-about-mesotunnels-and-biological-controls-cucurbit-crops
- Damman, K., and Pethybridge, S. 2021. “What do Farmers and Researchers Think About Mesotunnels and Biological Controls for Cucurbit Crops? Responses from 2020 surveys”, by Nieyan Cheng, and Dr. Wendong Zhang. Link: https://www.cucurbit.plantpath.iastate.edu/post/what-do-farmers-and-researchers-think-about-mesotunnels-and-biological-controls-cucurbit-crops
- Gleason, M.L. 2021. Looking back at Iowa field trials in 2020. Link: https://www.cucurbit.plantpath.iastate.edu/post/looking-back-iowa-field-trials-2020
- Badilla, S. 2021. Do's and don'ts when using mesotunnels in commercial organic acorn squash production” Link: https://www.cucurbit.plantpath.iastate.edu/post/dos-and-donts-when-using-mesotunnels-commercial-organic-acorn-squash-production
- TWITTER:
- Average number of profile visits per month, January-October 2021: 240. Average number of Impressions per month: 850.
- YOUTUBE CHANNEL: 14 videos posted in 2021; total views by November 22, 2021: 217. Link: https://www.youtube.com/channel/UCjyDwtnC4FDGKz1PU2QKrVw
- JOINT VIDEOS WITH ISU-IPM CHANNEL: 14 videos; total views by November 22, 2021: 1,432. Link: https://youtube.com/playlist?list=PLU1nNyLMXXaN-5tWuNbogkvJ4gLvpMCX3
- LINKED IN:
- Jan, 2021. Video post: an introduction to "Resilient systems for sustainable management of cucurbit crops" – 239 views.
- Feb, 2021. Video post: Ajay Nair on mesotunnel effect of cucurbit crop growth and microclimate: on-farm trials in Iowa, 2020. 185 views.
- Mar, 2021. Blog post: Reflecting on the 2020 preliminary results of the mesotunnel system in NY. – 87 views.
- April, 2021. Video post: Interview with Jordan Scheibel: on-farm cooperator from Iowa. 148 views.
- May, 2021. Posted the Solutions from the Land publication. 177 views.
- June, 2021. Posted the mesotunnel’s infographic. 508 views.
- August, 2021. Posted the video: “5 things you didn’t know about muskmelons”. 799 views.
- August, 2021. Posted video: “Are row covers (mesotunnel) treatments modifying the growth cycle of muskmelon?”. 287 views.
- September, 2021. Posted a Twitter post about the field day at Scattergood farms. 123 views.
- September, 2021. Posted a notice on the release of The Current Cucurbit podcast. 311 views.
- October, 2021. Posted Ep04 of the podcast series. 259 views.
- October, 2021. Posted video: “How to optimize organic weed control”. 624 views.
- November, 2021. Posted Ep07 of the podcast series. 82 views.
- IFVGA NEWSLETTER: “What’s a mesotunnel and what’s it good for?”. Date: June, 2021. Link: https://mailchi.mp/3e3a78b845ec/ifvga-news-updates-4940949?e=%5bUNIQID
Project Activities
Educational & Outreach Activities
Participation Summary:
On-farm demonstration trials.
- Iowa. An on-farm trial was held at Middle Way Farms, Grinnell, Iowa; grower-cooperator was Jordan Scheibel.
This project focused on the use of mesotunnels for integrated insect management in sustainable vegetable production. An on-farm trial grower-collaborator trial was established at Middle Way Farms, Grinnell, IA. The farm is owned and operated by Jordan Scheibel. The farm is a small, chemical-free, direct market vegetable farm just outside of Grinnell, Iowa, selling seasonally May through December to customers in Grinnell, Newton, and the surrounding area.
Growing season: The research focused on utilizing watermelon as a crop to test and compare ProtekNet vs. no-cover treatment. Due to inclement weather and a wet spring planting was delayed. Three week old watermelon seedlings were transplanted on raised black plastic mulch beds on 3 July 21. Treatments included a no-cover and ProtekNet. The ProtekNet netting was installed on 6 July 2020. Each treatment was 40 ft. long and there were three replications for each treatment. ProtekNet were removed on 9 August 2020 to facilitate pollination. One-time harvest was conducted on 13 October 2020.
There was no difference in marketable fruit number or weight between treatments (Table 1). Marketable fruit count ranged from 21 to 23 and weight ranged from 93.2 to 99.4 lbs. Insect damage was recorded on the fruit at the time of harvest but there were no differences between treatments. Overall, the yield from the entire study was low and this is due to the damage caused to the plants by Derecho storm which took place on 10 August 2020. Many of the plants had severed stems and were damaged by the hail that was part of the Derecho.
Air temperature data was continuously collected during the growing season using Hobo sensors (Onset Data Loggers, Bourne, MA). There were no significant differences in air temperature between treatments for the month of July (Table 2). There were significant differences in light intensity between treatments for the month of July with Protek net reducing light intensity by 25% (Table 2). We also collected grower feedback on plant vigor, difference in insect damage and pest pressure, ease of installation, management challenges, and cost associated with Protek net treatments.
Based on the feedback from Jordan, ProtekNet treatments could have provided the benefit of insect protection if the crop was planted earlier, typically beginning of June. In 2020, the crop was planted in July when major insect pests had already taken hold on other crops. Also, since the farm was not able to reinstall the ProtekNet after pollination, all treatments were exposed to the insects and other environmental factors. The major setback was the Derecho event which did not allow for a fair comparison of the treatments as the entire study was heavily impacted.
Another challenge was to manage weeds in the ProtekNet treatment (Fig. 2). Although the farm applied straw mulch between rows, the thickness of the application was not enough to stop weeds from emerging. One of the strategies moving forward could be the use of weed fabric between rows where Protek net treatments are being installed.
- In 2021, Iowa on-farm demonstration trials were held at 1) Scattergood Farm near West Branch, 2) Humble Hands Harvest Farm near Decorah, and 3) Blue Barrel Farm near Cuba City. All three trials compared production of butternut squash in three regimes: mesotunnels; low tunnels; and non-covered. Each trial had three replications (25- or 50-ft-long rows) per treatment. All three farms used ProtekNet as the mesotunnel fabric, with landscape fabric installed between rows for weed control. At Blue Barrel Farm, the mesotunnel and non-covered treatments has significantly higher marketable yield than the low-tunnel treatment. At Humble Hands Harvest Farm, the mesotunnel treatment had significantly higher yield than the non-covered treatment, and the low-tunnel treatment had significantly lower yield than the other two treatments. These results emphasize that mesotunnel systems have potential to increase yields of cucurbit crops other than muskmelon, although economics of this approach need to be compared with other organic strategies.
- Missouri. An experiment was conducted with 'Athena' muskmelon at the Organic Farm of Lincoln University in summer 2020. The experimental design was a randomized complete block design with 2 treatments (non-covered control and mesotunnel); 3 sections; 3 blocks per section and 10 plants per block. Transplanting took place on June 12. Cucumber beetle populations were extremely low, and bacterial wilt symptoms were not evident in the field. Statistical analysis of the yield data has not been done yet. No educational events were held in 2021 due to COVID-19 restrictions.
Learning Outcomes
- IPM for organic muskmelon growers in Iowa and Missouri
Project Outcomes
Farmers gained practice with using mesotunnel systems for cucurbit crops in cooperation with Iowa State project team personnel.
- Weed management in mesotunnel systems. We think we are making progress in optimizing the use of teff, an ancient cereal species, for weed control in the alleys between plastic-covered crop rows in mesotunnel systems for organic muskmelon production. Our 2021 results showed that timely mowing of teff in the alleys, about 3 weeks after transplanting, suppressed weeds effectively but did not suppress muskmelon yield. This 1-year, one-site result, however, needs to be backed up with additional years of trials before teff guidelines can be recommended for organic cucurbit growers. Landscape fabric is a viable alternative that controls weeds nearly 100%; however, the fabric is laborious to install, remove, and store between seasons, and its cost-benefit needs to be further defined. Further weed management trials under mesotunnels are planned for 2022.
- Pollination in mesotunnel systems. Our research results in Iowa u have led to the preliminary conclusion that, for organic muskmelon, the "full season" strategy, which keeps mesotunnels closed all season except for inserting purchased bumble bees, consistently out-yielded strategies that temporarily removed the nylon netting (entirely or just the ends of the rows) for 2 weeks to allow pollination had lower marketable yield. Further (2022) field experiments, on-farm demonstration trials, economic analysis, and grower surveys will further clarify which pollination strategies have the most potential for organic muskmelon in Iowa.