Sustainable Pest Management Approaches for High Tunnel Screenhouse Production in the Tropics
We had constructed 6 screenhouses for five vegetable farms. At each farm site, farmers selected their vegetable crops of interest to grow inside the screenhouse (SH) and compared to that grown in open fields (OF). Crops being tested by the farmers include tomato, aquaponic cucumber, water melon, pumpkin, chili pepper, and kale. Farmers were educated on “Turn-the-Page” weed mat method for weed control, “Adopt the Insectary” method to introduce beneficials insects and pollinators into the screenhouse, and “Trap Crop + biofumigation” methods to manage nematode pests in the screenhouse. The participating farmers received one to one assistance from our team to install the screenhouse using affordable materials. A local distributor for 16-mesh screen materials to build the insect exclusion screenhouse was identified in Hawaii. The first farmer whom we built the screenhouse with is very impressed with the results and is planning to construct another one on his own. Since the first screenhouse was built for this project, two newer screenhouse designs were built to 1) reduce construction price, and 2) better adopt the beneficials into the screenhouses for pest management. A total of 4 screenhouses of 15X50 square ft, one with 15X30 square ft and one with 15X30 square ft in hoop house design were built. Two parthenocarpic cucumber trials conducted to compare insect damage and cucumber yield between screenhouse vs open field production revealed total crop failure due to fruitflies and pickle worms in the open field, vs 90,151 lb/acre of marketable Persian cucumber inside the screenhouse were harvested. Three field trials conducted to examine the efficacy of weed mat covering with “Turn-the-page” method for weed control revealed that a minimum of 3 weeks coverage in combination with irrigation weed flushing suppressed grasses and broadleaf weeds effectively. However, this weed management technique is mostly suitable for transplanted rather than direct seeded crops. This is because weeds eventually out grown the direct seeded plots but not the transplanted plot in the “Turn-the-page” treatment. A graduate student screened 8 oil radish varieties to select the most suitable variety for “Trap crop” and “Biofumigation crop” against root-knot nematodes and determined that oil radish ‘Sod Buster’ to be the most promising variety against root-knot nematodes. Since the beginning of this project, we had reached out to 36 vegetable farmers in Hawaii through the new farmers training programs (GoFarm Hawaii), college classroom lectures, 6 on-farm visits to local vegetable growers to construct screenhouse, organized a sustainable pest management workshop for vegetable growers (attended by 120 people) and generated a website to post “Sustainable Pest Management Approaches” related to this project.
Specific objectives of this proposed project are to:
- Compare crop yields and market values of produce from screenhouse (SH) vs open field (OF) production of each farmers.
- Monitor insect pest damage (pickle worm and fruitflies for squash, incidence of virus on tomato, flea beetle damage on eggplant, rose beetles on taro, imported cabbage worm or diamond back moth damage on lettuce), weed pressure, and nematode population densities in SH vs OF production.
- Evaluate the suppression of root-knot nematode population densities following “Dead-end Trap Crop” practice.
- Scout for diversity of beneficial insects visiting cash crops in SH vs OF production.
- Conduct workshops and field day events for “Do-it-yourself (DIY) screenhouse construction”, “Turn the Page”, “Adopt the Insectary” and “Dead-end Trap Crop” methods and evaluate farmers’ perception, adoption, and record their suggestion/inputs on the project. These workshops will be repeated for the University of Hawaii new farmers training program, GoFarm Hawaii, as part of their on-farm training lectures.
A total of 6 screenhouses were built in 5 vegetable farms in Hawaii. Three screenhouse’s designs were constructed based on special need of each farmer (Fig.1, 2, 3). Different field trials were conducted to achieve milestones for each objectives.
Objective 1: We conducted a cucumber trial in a screenhouse at the Poamoho experiment station where we grew parthenocarpic Persian cucumber GVS 603 (Golden Valley Seed, El Centro, CA) and compared cucumber yield obtained from plants grown in open field outside of the screenhouse (Fig. 4, 5). Cucumber fruits produced in open field were all damaged by melon flies or pickle worms (Fig 6) and resulted in no marketable fruits. Whereas 90,151 lb/acre of marketable Persian cucumbers were harvested from the screenhouse (Fig. 7) planted at same densities and same time. However the field site was heavily infested with root-knot nematodes (Fig 8). When oil radish (Fig. 9) was planted prior to cucumber planting, cucumber yield was 20% higher than that produced in field plot not planted with oil radish. Thus, farmers not only have additional oil radish for harvest (Fig. 10) but also improved cucumber yield possibly due to green manure effect or “Trap crop/biofumigation” effect against the root-knot nematodes in the screenhouse. The oil radish was terminated by using no-till (Turn-the-page” weed mat covering method) (Fig. 11) where the leaf residues of oil radish was return to the field and cover with weed mat for two weeks. Weed mat was removed prior to cucumber planting. This experiment also demonstrated the use of “Adopt the insectary plants” approach by planting insectary plants right outside of the screenhouse (Fig. 12) to attract beneficial insects including pollinators and parasitoid wasps. One side of the screenhouse wall can be opened (Fig. 12) when the targeted pest population is not at risk (pickle worms are more active at night, thus, the screenhouse can be open during the day time especially when pollination is needed at the cucumber flowering stage). This approach allow farmers to not having to rely on seeds of parthenocarpic varieties which are very expensive. Alternatively, farmers could also plant insectary plants like buckwheat inside the screenhouse (Fig. 13) to practice the “Adopt the insectary plants” method by opening one side of the screenhouse wall. This approach allow beneficial insects to prey on smaller insect pests inside the screenhouse. Pumpkin grown with this screenhouse with insectary plants had minimal pickle worm damage (Fig. 14). Farmer Anthony Deluze said that “I think the screenhouse has been an awesome tool and love the design. I’m trying to figure out as soon as possible how to fund another screenhouse in my farm”. Although his screenhouse did not protect his cherry tomato from tomato yellow leaf curl virus (TYLCV) transmitted by whiteflies, when he grew ‘Nyagous’ which is resistant to TYLCV, he had greater yield inside the screenhouse than in the open field due to less fruitflies, pin worms and bird damage (Fig. 15). Mele Judd (Fig. 16) and Dan Ching (Fig. 17) were both very excited to grow cucurbit crops in their screenhouse with a control open wall for their organic production land and aquaponics production, respectively. They were previously challenged by fruitflies and pickleworms and were not able to grow any cucurbit crops before. A video capture how we construct the screenhouse with open wall can be seen in this vimeo video https://www.youtube.com/watch?v=cBP52egYG9s. Jay Bost (Fig. 18) see the potential of growing bell pepper and eggplant beside cucurbit crops for the GoFarm Hawaii New Farmers training program to help them cope with pepper weevils and flea beetles. When the Hawaii Farm Bureau heard about this affordable screenhouse construction project, they approached us to build a screenhouse with funding from another grant as seen in this vimeo video https://www.youtube.com/watch?v=EU5uFxW98Ng. Thus our project has reached out to a wider audience through Hawaii Farm Bureau Association.
Objective 2: We conducted three field plot experiments during the fall of 2015 to examine the efficacy of weed mat covering or we referred to it as “Turn-the-Page” weed covering method for weed control. It was determined that weed covering with the weed mat for three weeks only suppress initial weed population for 3-4 weeks after a cash crop (corn) was planted. However, if the weeds were to be “flushed” out by fertilizer prior to covering with weed mat, then weed suppression could last till the end of a corn crop. None-the-less, when transplant seedlings into “Turn-the-page” plot, crops can out compete weeds. Thus, showing a good weed control method without tilling the field. This would be helpful to operate in a screenhouse cropping system where heavy machinery inside the screenhouse is difficult. A student summarize the experiments conducted and present at the 2016 College of Tropical Agriculture and Human Resources (CTAHR) Student Research Symposium. Step by step instruction to conduct “Turn-the-page” is posted in this flickr page: https://www.flickr.com/gp/125718267@N02/77M9mo.
Objective 3: A graduate student screened eight oil radish varieties for trapping and biofumigation effect against root-knot nematodes. ‘Sod Buster’ was determined to be the best variety for “nematode trap crop and biofumigating effect.” A poster summarizing the results was presented at the 2016 CTAHR Student Research Symposium. Field experiment is ongoing to determine best timing to terminate the trap crop for effective nematode suppression.
Objective 4. A field trial was conducted to compare kale damage by various Lepidopteran caterpillars on kale grown inside and outside of a screenhouse at the Waimanalo Experiment Station. Kale grown in the screenhouse had significantly less caterpillar damage compared to that grown in open field during the first two month of growth. Results are presented in a power point presentation to 120 participants attending a Mini Vegetable Conference for Oahu on May 24, 2016 available at http://www.ctahr.hawaii.edu/WangKH/Downloads/2016_Organic_SPM.pdf. However, eventually thrips population increased significantly inside the screenhouse. This justified the need of allowing beneficial insects to come into the screenhouse for future studies.
Workshops/Guest Lectures for GoFarm Hawaii training program
- Wang, K.-H, J. Sugano, J. Uyeda, S. Ching, J. Kam, T. Radovich, S. Fukuda. Organic and sustainable pest management options. Advancing Oahu’s Edible Crop Industries-Mini Conference. Turtle Bay Resort Turtle Bay, HI. May 24, 2016. (Attendance: 120).
- Wang, K.-H. Cover crop and pest management. GoFarm Hawaii at Windward Community College, April 20, 2016. (12 students).
- Wang, K.-H. Cover crop and pest management: Lecture and field scouting. GoFarm Hawaii at Leeward Community College, Feb 27, 2016. 12 students.
- Wang, K.-H., J. Uyeda, S. Migita, J. Marquez, Philip Waisen, G. Nagai, S. Mishra. AgExposure: Working at Poamoho Experiment Station, GoFarm Hawaii at Leeward Community College (LCC), December 5, 2015, 20 students. http://www.gofarmhawaii.org/blog/agxposure-at-ctahr-poamoho
- Domen, B. and -H. Wang. Turn-the-page weed mat covering for weed management in a no-till cropping system. CTAHR Student Research Symposium, Honolulu, HI. April 8, 2016.
- Waisen, P. and -H. Wang. Screening oil radish (Raphanus sativus) varieties for nematode management through trap cropping and biofumigation effects. CTAHR Student Research Symposium, Honolulu, HI. April 8, 2016.
- Screenhouse with retractable wall to adopt beneficials (produced by Jensen Uyeda)
- Screenhouse production with PVC Hoops (produced by Jensen Uyeda)
Impacts and Contributions/Outcomes
Besides constructing a total of 6 screenhouses for the participants on this project, which contributes to ~4000 ft2 of screenhouses, we anticipate more farmers would be constructing screenhouses on their own. We expect a ripple effects when farmers visiting each other or through the words of mouth. We are still finalizing the extension article to provide detail instruction for farmers to construct screenhouse using designs from this project. However, initial survey collected after the Mini Vegetable Conference organized by our team at Turtle Bay on Oahu, May 21, 2016 revealed great interest in screenhouse production. The survey also reflects great interest in sustainable pest management approaches such as insectary plants, screenhouse and border crops. Our collaborative farmers already plan on expanding screenhouses in their farms beside the one that was constructed for them. Many organic farmers like to get a premium price for their produce. The screenhouse production helps them to overcome some challenging pests. One grower was able to grow high value heirloom tomatoes to supply to high end restaurant chains, which will allow him to get supplies to build more screenhouses. At least 10 students had been participating in this screenhouse project which provided them hand-on training, experience to interact with farmers. The students also help to evaluate pest suppressive effect on various vegetable crops. We anticipate a reduction in the problem of pesticide resistant pest population (especially those that develop resistance to Bt), and reliance on tillage of herbicide for weed control for short-term vegetable crops, while increase in awareness of organic approaches for nematode management. There should be an increase of the use of screenhouses for vegetable production in Hawaii as our affordable screenhouse construction could reduce cost >10 times compare to buying a premade screenhouse to ship from companies out side of Hawaii. The novel design of screenhouse with open wall also bring awareness to the need of providing insectary plants for pollinators and other beneficial insects into agroecosystems. This could reduce the stereo type behavior of using pesticides or tillage for insects, weeds and nematodes control. Our lectures given to new farmers training program (GoFarm Hawaii http://www.gofarmhawaii.org/) bring awareness of ecological based pest management approaches so that farmers should be more open minded on less pesticide use.
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