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United States Department of Agriculture

Agricultural Research Service

Research Project: Pre and Postharvest Treatment of Tropical and Other Commodities for Quarantine Security, Quality Maintenance, and Value Enhancement

Location: Tropical Crop and Commodity Protection Research

2013 Annual Report

1a. Objectives (from AD-416):
The long term goals of our research program are to develop and protect U.S. export markets for fresh tropical commodities with emphasis on expanding and diversifying agriculture and agricultural exports in Hawaii and other states by providing environmentally sound, economically viable systems, treatments, or processes that control quarantine pests, ensure product quality and food safety, and increase product value while safeguarding the agriculture of other states. Our research will address three objectives over the next 5 years: (1) Develop new or improved postharvest treatments, including alternatives to methyl bromide, for tropical fruit, vegetable, and ornamental crop exports to ensure security against quarantine pests and to meet quarantine requirements of U.S. trading partners; (2) Develop new or improved postharvest treatments for tropical fruit, vegetable, nut and ornamental crops to improve product quality and shelf life, reduce or eliminate postharvest disorders or decay, and enhance product value; and (3) Identify, develop or improve preharvest methods for tropical fruit, vegetable, nut, and ornamental crops that enhance postharvest quality and reduce the incidence of quarantine pests that limit exports.

1b. Approach (from AD-416):
The approach is to develop quarantine treatments, such as low dose irradiation and hypobaric treatments, and other mitigation techniques for fresh tropical commodities and ornamental crops. Quarantine irradiation treatments will be developed for light brown apple moth, papaya mealybug, and green scale. Optimum hypobaric treatment parameters for controlling Caribbean fruit fly, Mediterranean fruit fly, oriental fruit fly, and melon fly will be determined. We will establish the tolerance of tropical fruit to any new or modified quarantine treatments, including the quality of diverse assortments of tropical fruit following irradiation treatment. To expand markets for high-value specialty fruit, we aim to develop postharvest disease control and packaging strategies to extend shelf-life. Also, preharvest practices that reduce the incidence of quarantine pests that limit exports will be investigated, such as non-chemical alternatives to control thrips on orchids, essential oil formulations for control of waxy insects on ornamental crops, and biological control of white peach scale on papayas. Formerly 5320-43000-015-00D (12/10).

3. Progress Report:
This research project develops preharvest and postharvest treatments or systems to control quarantine pests, while retaining the quality and shelf-life of tropical crops. The project supports the expansion and diversification of U.S. exports of fresh tropical crops, while protecting U.S. agriculture from pest incursions. An irradiation treatment, 150 Gray Units (Gy) was developed for light brown apple moth eggs and larvae to supply Hawaii and California with a quarantine treatment alternative if other countries or states impose restrictions on exported fresh produce. An irradiation treatment (80 Gy) for spotted wing drosophila, a new invasive pest spreading across the U.S., is currently undergoing large-scale validation testing. A radiation dose of 90 Gy sterilized queens of big-headed ant, little fire ant, and Argentine ant suggesting this dose is sufficient to control ants hitchhiking on exported fresh commodities. Basil oil fumigation was shown to sensitize rice weevil and Aspergillus and Penicillium molds to irradiation treatment, potentially allowing for the use of lower and less costly doses to control the pests in stored grains. Modified atmosphere packaging produces a low oxygen atmosphere that may increase the radiation tolerance of pests during quarantine irradiation treatment. Tests with melon fly and Mediterranean fruit fly in papaya demonstrated that the 150 Gy generic radiation dose for fruit flies was not compromised when using MAP. The quality of irradiated produce determines market acceptance. High-value mixed fruit boxes of papayas, bananas, dragon fruit, and pineapples were irradiated at 0, 400 and 800 Gy and evaluated for quality after treatment, storage, and ripening. Papayas and dragon fruit tolerated x-ray radiation at 800 Gy. The tropical fruit had similar radiation tolerance when treated as single or mixed fruit boxes. Ionizing Irradiation also is a potential method for controlling spoilage micro-organisms and extending shelf-life of fresh-cut produce. Doses up to 1000 Gy were effective at reducing microbial populations while maintaining the physical and nutritional quality of minimally processed, purple-fleshed sweet potatoes during two weeks of storage at 4°C. For coffee berry borer (CBB) control, we monitored cumulative infestation levels over the season using Mexican CBB traps and continued on-farm research to determine effective concentrations and persistence levels of Beauveria bassiana for management of CBB. Field releases of the white peach scale parasitoid Encarsia diaspidicola were made for the first time in Hawaii papaya orchards, and the parasitoid appears to have established.

4. Accomplishments
1. Irradiation quarantine treatment for rice weevil. The primary source of storage loss in rice in terms of weight and sensory quality is the rice weevil, Sitophilus oryzae (L.). Irradiation is a quarantine treatment option for stored products pests such as rice weevil. ARS scientists in Hilo, Hawaii, determined that an ionizing radiation dose of 120 Gray units (Gy) applied to 38,025 adult weevils in rice resulted in no reproduction and minimal weight loss of rice. Irradiation at 120 Gy will provide quarantine security for rice weevil, and prevent post-irradiation weight loss caused by insect feeding in the commodity. Resistance to phosphine fumigation is a critical issue for control of stored products pests including rice weevil. Irradiation is a feasible alternative to fumigation to control rice weevil populations, and will help manage resistance to phosphine by preventing the spread of resistant insects in exported grains.

2. Shelf life extension for fresh-cut sweet potatoes using x-ray radiation treatment. Fresh-cut sweet potatoes are a value-added product that offer convenience and nutritional quality to consumers and institutional markets. Ionizing radiation is a potential method for controlling spoilage micro-organisms and extending shelf-life of fresh-cut produce. ARS scientists in Hilo, Hawaii, determined that x-ray radiation treatment at doses up to 1000 Gray units (Gy) were effective at reducing microbial populations while maintaining the physical and nutritional quality of minimally processed, purple-fleshed sweet potatoes during two weeks of storage at 4°C. Adoption of the radiation treatment will diversify markets for the industry and provide consumers with fresh, healthy, value-added sweet potato products.

3. Evaluating the effects of modified atmosphere packaging on fruit fly radiation tolerance. Modified atmosphere packaging (MAP) produces a low oxygen environment that can increase produce shelf life. However, low oxygen is known to increase insect tolerance to irradiation, and the use of MAP with products treated by irradiation before export to control quarantine pests may inadvertently compromise treatment efficacy. Melon fly third instars were placed in papayas and sealed inside various MAP films with different permeabilities to oxygen. Melon fly survival to the adult stage was increased only in the MAP producing the lowest oxygen concentration (Ziploc bags, 1-4% oxygen) at 50 Gray units (Gy), and this MAP product was selected for further testing at higher radiation doses. In large-scale tests, 9,000 melon fly larvae infesting papayas in Ziploc bags were irradiated at 150 Gy with no survivors to the adult stage. MAP can increase insect survivorship during irradiation treatment at certain doses and oxygen concentrations, but should not compromise the efficacy of the 150 Gy generic radiation treatment approved for tephritid fruit flies.

4. Processing quality of fermented Noni juice. Noni (Morinda citrifolia) is a tropical plant for which the fruit and juice extracts are reportedly therapeutic for diabetes, hypertension, and certain types of cancer. Noni juice is available as a nutritional supplement in the marketplace, but the processing of noni lacks standardization. Consequently, juice products may vary in chemical, physical and microbial properties depending on the processing method and duration. ARS scientists in Hilo, Hawaii, determined the microbial and chemical properties of fresh and fermented noni juice. Major changes in fungal and bacterial populations, sugars, organic acids, and ethanol were quantified during the fermentation process. The optimum fermentation time was 14 to 21 days, and the need for pasteurization was clearly demonstrated. These results will be useful in developing a standard method for producing consistent quality noni juice.

Review Publications
Sivakumar, D., Wall, M.M. 2013. Papaya fruit quality management during the postharvest supply chain. Food Reviews International. 29(1):24-48

Oner, M.E., Wall, M.M. 2012. Processing conditions for producing french fries from purple-fleshed sweetpotatoes. Transactions of the ASABE. 55:2285-2291.

Follett, P.A., Snook, K. 2012. Irradiation for quarantine control of the invasive light brown apple moth, Epiphyas. Journal of Economic Entomology. 105:1971-1978.

Manton, J.L., Hollingsworth, R.G., Cabos, R.Y.M. 2012. Potential of Steinernema carpocapsae (Rhabditida: Steinernematidae) against Hypothenemus hampei in Hawaii (Coleoptera: Curculionidae). Florida Entomologist. 95(4):1194-1197.

Phytosanitary irradiation for fresh horticultural commodities: Research and regulations. In C.H. Sommers and X. Fan eds., Food Irradiation Research and Technology (Revised 2nd edition). Blackwell Publishing, Ames, Iowa. 225-252.

Last Modified: 06/22/2017
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