Sustainable Pest Management Approaches for High Tunnel Screenhouse Production in the Tropics

View the project final report

• 2016 annual report
• 2017 annual report

Commodities

• Vegetables: cucurbits, eggplant, greens (lettuces), tomatoes

Practices

• Crop Production: high tunnels or hoop houses

Hawaii, along with other Pacific islands, is located in the most geographically isolated area from any continents in the world. Currently over 80% of food and 90% of energy in Hawaii are imported (Leung and Loke, 2008). Food security and self-sustainability are top priorities of concern in a developing new generation of farming communities. While farmers in the tropics are taking advantage of a climate that allows for year-round crop production, they are also severely challenged by continuous crop pest pressure that otherwise would have a winter dormancy period in the temperate zone. Due to the growing environmental consciousness among consumers and the growers, organic farming approaches are gaining popularity. However, organic farmers in Hawaii listed “lack of information on effective, organic insect pest management and how to attract and identify beneficial insects” as the top priority research needed (Radovich, 2009). This prompted us to design this project to evaluate the profitability of high tunnel screenhouses for crop production so as to eliminate the necessity of pesticide applications.

Co-PIs on this project had developed affordable protocols to construct high tunnel screenhouses using home improvement store supplies (http://www.ctahr.hawaii.edu/WangKH/Downloads/P-DIY-screenhouse.pdf). When using 60-mesh nylon netting, the high tunnel provides a barrier for virus transmitting insects as small as aphids or whiteflies. The advantages of reduced pesticide applications and increased crop yields are shown by scientists in Spain comparing screenhouse with open field production (Romeo-Gámez et al., 2011). With an estimated cost of $1,450 for supplies to set up a 14×200×8 ft³ screenhouse, farmers can see a return on their investment within a few cropping cycles. We foresee the significant impact of this farming technique on ensuring organic production of multiple vegetable crops, such as tomato that are suppressed by insect transmitted viruses; cucurbit crops that are affected by pickleworms and fruit flies; strawberry, eggplant, taro, and others that are damaged by rose beetles, oriental flower beetles, and flea beetles; and leafy greens that are damaged by diamond back moth or imported cabbage worms.

Unfortunately, high tunnel screenhouse crop production has several challenges. Pollination maybe compromised which is a problem for cross pollinated crops. In addition, natural enemies such as parasitic wasps, lady beetles, hoverflies, lacewings, and so on will also be excluded, creating a risk of pest outbreak if the insect pests were to get in. The problem would be greater for organic producers that rely on mechanical weed management. With the screenhouse structure installed, farmers will be restricted to a hand held rotovator or weed wacker which is more labor intensive than tractor driven rototillers. The difficulty of soil tillage in these structures could aggravate nematode problems. Organic farmers in Hawaii deal with plant-parasitic nematodes by growing a cover crop, sunn hemp, which produces nematode allelopathic compounds when soil incorporated. Clearly, whole-system sustainable pest management strategies need to be developed for high tunnel screenhouse production.

We are proposing to use the sequential weed mat covering approach known as “Turn the Page method” (TTP) developed by co-PI, DeFrank, who is a weed scientist. A detail demonstration on this approach was presented at the Worldwide Farmers Exchange Trainees Conference held on October 29, 2014 in Maui and is documented at http://www.ctahr.hawaii.edu/deFrankJ/NON_HOMEPAGE_PAGES/Maui_WFE_JD_2014.htm#Maui_WFE. The concept is killing existing weeds or cover crops after initial weed wacking in a portion of the field by covering the soil with a light excluding tarp for one to six weeks depending on weed types and then plant cash crops with no-till. Crops are planted in the freshly uncovered areas while the tarp (or page) will be moved (or turn) to the adjacent weedy areas. Thus TTP offers a sequential weed management tactic without herbicide and tillage and avoids covering the entire screenhouse with expensive woven weed mat. Farmers can sequentially cover a quarter of the house at biweekly intervals and plant their crop sequentially.

To address the issues of pollinators and beneficial insects being excluded by screenhouse, we propose “Adopt the Insectary” method. PI Wang had evaluated several insectary plants and developed insectary settings to attract pollinators and beneficial insects in Hawaii. Buckwheat and cilantro provide abundant pollen and nectar source for bees, hoverflies, and wasps; Pigeon pea is a perennial that attracts lady beetles over a long period; Scarlet milkweed is a host for yellow aphids which are not pests for vegetable crops but are attractive to aphid parasitoids; Sunn hemp and pigeon pea attract Lycaenidae butterflies which are not vegetable pests but draw Trichogamma wasps to parasitize their eggs; Sunn hemp also attracts alternative pollinators such as carpenter and leaf cutter bees (Wang, 2012). Installing wasps nesting blocks (Wang and Tavares, 2013) or bunched up cut bamboo sticks could serve as traps for these pollinators. Installing insectary gardens adjacent the high tunnel screenhouse in the open field for one month, then flipping the edge of the screenhouse to "adopt” the insectary settings into the screenhouse would establish beneficials inside.

We then propose to use oil radish as a “Dead-end Trap Crop” to trap root-knot nematodes. Oil radish is susceptible to root-knot nematodes, but if terminated within four weeks of growth, the nematode eggs cannot fully develop and thus trapped inside the roots, preventing them from attacking crop roots. Oil radish can be killed using TTP method.

Through farm demonstrations, we anticipate this multi-tactic approach for high tunnel screenhouse production can help farmers reducie pesticide use while sustaining viable organic crop production in Hawaii.

Five participating farms will join our demonstration and evaluation activities of this “Sustainable Pest Management Approaches for High Tunnel Screenhouse” project. A skilled technician will guide farmers to install screenhouses. At each farm site, farmers will select their vegetable crops of interest (zucchini squash, tomato, eggplant, taro, or lettuce) to grow inside the screenhouse (SH) as well as in the open field (OF) conditions. All farmers will go through trainings on “Turn the Page,”, “Adopt the Insectary,” and “Dead-end Trap Crop” methods organized by the PIs and receive one-on-one assistance during the first installation process. Specific objectives of this proposed project are to:

1. Compare crop yields and market values of produce from SH vs OF production of each farmers by repeating at least once in each location.
2. 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.
3. Evaluate the suppression of root-knot nematode population densities following “Dead-end Trap Crop” practice,
4. Scout for diversity of beneficial insects visiting cash crops in SH vs OF production.
5. 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 and 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.

Performance targets:

This will be a two-year project. We anticipate taking approximately four months to complete each trial pending on the crop selected. In all trials, pre-plant treatments for SH production is required. These include: two weeks of TTP to manage weeds, three weeks of “Dead-end trap crop” of growing oil radish to trap root-knot nematodes, one week of TTP to terminate oil radish. Five participating farmers agreed to join our demonstration trial. These include Jay Bost who will grow cucurbit crops at Waimanalo, Dan Ching who will grow lettuce and pak choi at Waianae, Anthony Deluze who will grow taro, Meleana Judd-Cox who will grow cucumber, and Chai Yoshimura who will grow tomato. Thus, it would take about 20 months or more to complete these five trials. This will leave us four months in between or at the end to write up extension publications, generate outreach media (education videos), webpage, field days and workshops, and analyze the data collected from each field trials as well as surveys for the final publication.