Project : USDA ARS

ARS Home » Pacific West Area » Hilo, Hawaii » Daniel K. Inouye U.S. Pacific Basin Agricultural Research Center » Tropical Crop and Commodity Protection Research » Research » Research Project #429226

Research Project: Pre-and Postharvest Treatment of Tropical Commodities to Improve Quality and Increase Trade Through Quarantine Security

Location: Tropical Crop and Commodity Protection Research

2020 Annual Report

Objectives
The long-term goals of our research program are to develop and protect U.S. export markets for fresh tropical commodities. An emphasis is placed 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 increase product value while safeguarding the agriculture of other states. Our research will address four broad objectives over the next 5 years: Objective 1: Develop new or improved postharvest treatments or technologies for fresh tropical commodities to ensure security against quarantine pests, including new irradiation treatments for western flower thrips, and various ants on fresh fruits. Sub-objective 1A. Develop quarantine irradiation treatments for western flower thrips, coffee berry borer, rough sweetpotato weevil, and red imported fire ant. Sub-objective 1B. Develop a quarantine cold treatment for melon fly in citrus. Sub-objective 1C. Determine the effectiveness of hypobaric treatments against surface pests. Objective 2: Develop new or improved postharvest treatments or systems (such as hypobaric storage and modified atmospheres) to improve quality and extend shelf life of tropical horticultural crops subjected to quarantine treatment. Sub-objective 2A. Determine hypobaric storage conditions that retain quality and extend storage life of fresh tropical fruit. Sub-objective 2B. Develop combination treatments of modified atmosphere packaging and irradiation to retain quality of exported fresh papaya. Objective 3: Develop or improve preharvest methods for surveillance, detection, and control of invasive tropical plant pests of quarantine significance, such as coffee berry borer. Sub-objective 3A. Study the ecology of Cathartus quadricollis and other predatory flat bark beetles and explore ways to increase their role in suppressing coffee berry borer populations in coffee. Objective 4: Develop multiple-component systems approaches to decrease the severity of or need for commodity treatments. Sub-objective 4A. Quantify systems approaches for quarantine security of melon fly.

Approach
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 treatment will be developed for rough sweetpotato weevil, in sweet potato, western flower thrips, red imported fire ant, and coffee berry borer. Optimum hypobaric treatment parameters for maritime shipment of tropical fruits to preserve quality and extend shelf life will be determined. We will establish the tolerance of tropical fruits to any new or modified quarantine treatments.To expand markets for high-value tropical specialty fruit, we will develop postharvest disease and packaging strategies to extend shelf life. Integrated pest management strategies for coffee berry borer will focus on understanding the population dynamics and ecology of predatory flat bark beetles and improving rear-and-release systems. A cold treatment will be developed for melon fly in citrus. Also, a systems approach will be developed for melon fly control in covered tomatoes using mass trapping, protein baits and sanitation.

Progress Report
This research project develops pre-harvest 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. This is the final report for the project 2040-43000-017-00D “Pre- and Postharvest Treatment of Tropical Commodities to Improve Quality and Increase Trade Through Quarantine Security”, which has been replaced by new project 2040-43000-018-00D “Postharvest Protection of Tropical Commodities for Improved Market Access and Quarantine Security.” In support of sub-objective 1A, postharvest irradiation treatments were developed to control specific quarantine insect pests including European grapevine moth, light brown apple moth, rough sweet potato beetle, little fire ants, spotted wing drosophila, Western flower thrips, and coffee berry borer; data on treatment efficacy were submitted to USDA-Animal and Plant Health Inspection Service (APHIS) and the International Plant Protection Commission (IPPC) for approved treatments. Recommendations were also submitted to APHIS and the IPPC for generic doses for all tortricid moths [290 Gray (Gy)] and curculionid weevils (175) Gy. Postharvest irradiation treatments may help other fruit exporting countries overcome quarantine restrictions during fruit fly outbreaks. New Zealand is concerned about invasive fruit flies and their threat to the kiwifruit industry, an issue that also could affect the California kiwifruit industry. In laboratory cage and open field tests, gold and green cultivars of kiwifruit were shown to be poor hosts for melon fly, Mediterranean fruit fly and oriental fruit fly, with limited natural infestation in these fruits. The gold-fleshed kiwi cultivar softened as irradiation dose increased to 800 Gy, but sensory quality was unaffected. In fruit quality research, the differential tolerance of four apple cultivars to potential x-ray disinfestation for codling moth showed that ‘Royal Gala’ was the most susceptible cultivar, with flesh browning increasing after longer pretreatment storage times and as dose increased above 500 Gy. Other cultivars including ‘Jazz’, ‘Envy’ and ‘Fuji’ did not show damage after x-ray irradiation regardless of storage time and dose. Modified atmosphere packaging (MAP) creates a low oxygen environment that may increase radiation tolerance in quarantine insect pests. In support of sub- objective 2B, studies with Oriental fruit fly, Mediterranean fruit fly, and spotted wing drosophila infesting fruit in commercial MAP bags showed no loss of efficacy at APHIS-approved irradiation treatment doses, suggesting quarantine security will not be compromised by the low oxygen environment. For papaya, MAP using polymer-blend films with high moisture vapor transmission rates produced 1-3% carbon dioxide steady state levels within packages during storage at 10 degrees C, and 5-10% CO2 at 22 degrees C. Shelf-life (15.5 days) and quality were similar for control and MAP fruit, however MAP reduced fruit weight loss from 5.3% to 12.3%. In related research, a thyme and oregano oil extract embedded in methyl cellulose or chitosan films was shown to provide control of rice weevil, and Aspergillus and Penicillium molds in packaged rice, and the combination of treatment with irradiation showed synergistic effects. Effective fumigation treatments and protocols may help Hawaii ornamental crop growers overcome shipment rejections to the mainland and abroad due to quarantine restrictions. Ethyl formate fumigation was effective at killing various stages of western flower thrips and melon thrips in Hawaii without noticeable decrease in orchid shelf life. These thrips cause most of the rejections of cut orchid flower exports from Hawaii. Ethyl formate fumigation was also effective at controlling coconut mealybug and little fire ant, which are the main problems in cut ginger flower exports. In support of sub-objective 2A, hypobaric storage (low oxygen partial pressure) was ineffective at controlling insect pests but extended the storage life of mango and cherimoya fruit without loss of edible quality. Fruit storage life was extended 7 to 10 days for mango fruit and 10 to 12 days for cherimoya fruit under hypobaric conditions (2.7 kilopascals (kPa) pressure, 100% relative humidity (RH), and 13 °C) when compared to control fruit stored at 100 kPa. Fruit ripened normally after removal from hypobaric storage, but disease incidence after ripening was not inhibited in most trials. In support of sub-objective 3A, predator breeding stations were developed to augment biological control of the coffee pest, coffee berry borer (CBB). In the laboratory, breeding stations stocked with 100 Cathartus quadricollis adults and placed in sealed ventilated buckets were shown to produce 10,000 adults over four months, demonstrating the ability of the stations to augment predator populations on coffee farms. These stations are now available commercially and deployment could help suppress populations of coffee berry borer in Hawaii coffee. Another natural enemy of coffee berry borer, the parasitoid Phymasticus coffea, which attacks CBB adults, is under evaluation for efficacy and safety in quarantine. Parasitoids are being imported from a colony at Cenicafe in Colombia, and tested against various native and exotic scolytine beetles in Hawaii. Thus far, this parasitoid appears to be quite host specific, attacking only CBB, its congener the tropical nut borer Hypothenemus obscurus, an exotic pest of macadamia nut, and several other non-pest species of Hypothenemus. In coffee quality research supporting Objectives 2 and 3, an automated head space, gas chromatography, mass spectroscopy method (HS/GC/MS) was developed to compare volatiles in green coffee beans exhibiting various levels of visible damage by coffee berry borer. The relative concentrations of eight prominent volatiles were identified to be likely markers for CBB damage. In support of Objective 4, identification of little fire ant pheromone was initiated. Little fire ant inflicts a painful sting and is a pest in many agricultural crops in Hawaii, especially causing shipment rejections of exported ornamental and tropical fruit crops. Identification of the recruitment trail pheromone in little fire ant might help improve efficacy of toxic baits for this important urban and agricultural pest. In laboratory bioassays, chemicals in the Dufour’s gland of workers elicited trailing behavior in little fire ant workers. Hexane extracts of 1,000 Dufour’s glands were further fractionated and only dichloromethane and methanol fractions elicited trailing behavior, suggesting existence of potential trail pheromone components in those two fractions. In support of sub-objective 4A, insecticidal properties of erythritol (a non nutritive sugar) were explored. Erythritol ingestion increased mortality of Mediterranean fruit fly, oriental fruit fly, melon fly, and solanaceous fruit fly of Hawaii in a dose-dependent manner. Adult oriental fruit flies fed with 0.5M (moles/liter) sucrose + 2.0M erythritol solution invariably died within 6-10 days. Before they die, flies fed with erythritol laid significantly fewer eggs.

Accomplishments
1. Predator breeding stations for augmentative biocontrol of coffee berry borer. The Flat Beetle, Cathartus quadricollis, is a significant predator of CBB in Hawaii that may help suppress populations in unharvested coffee left on the tree between seasons and on abandoned farms. Predator ‘starter kits’ (buckets with food and predator beetles) were distributed to over 300 coffee growers. A commercial breeding station was developed with a commercial supplier using a pheromone to attract Cathartus quadricollis to a food source (cracked corn) where they feed, multiply, and disperse on the coffee farm. The commercial availability of breeding stations should facilitate grower adoption of predator augmentation technology and improve coffee berry borer control in Hawaii coffee.

2. Novel repellent for spotted wing drosophila. Semiochemical research identified a novel spotted wing drosophila (SWD) repellent made from microbes and fruit that significantly reduced SWD infestations of ripe raspberries, a preferred fruit host. This repellent is a food-grade flavor chemical, is safe, and is more effective than the previously identified SWD repellent 1-octen-3-ol. A commercial supplier of this repellent has been identified through a Cooperative Research and Development Agreement(CRADA). commercial availability of an effective repellent should facilitate grower adoption and more sustainable SWD management.

3. Export protocol for Hawaiian 'Sharwil' avocados. A systems approach was developed to export Hawaii ‘Sharwil’ avocados. The systems approach components are poor host status for Oriental fruit fly, hard mature green maturity stage, fruit fly monitoring, threshold-based field sprays, and export during winter months to northern states only. Exports have been steadily increasing each year and several growers are planting new avocado orchards to take advantage of the export program.

4. Quarantine irradiation treatment for hitchhiking ants. Ants can be problematic hitchhiker pests in exported fruits and vegetables that cause rejection or return shipment. Irradiation tolerance studies with ants were conducted for the first time, including the big-headed ant, little fire ant, Argentine ant, and red imported fire ant, to establish radiation doses to provide to regulatory officials at APHIS and California Department of Agriculture (CDFA). Queens of all species were sterilized at doses <125 Gy, suggesting that the commonly used generic dose for fruit flies (150 Gy) will also control any hitchhiking ants. The results were submitted to the International Plant Protection Convention (IPPC) for consideration as a phytosanitary treatment.

5. Sterile insect technique (SIT) for small hive beetle. Small hive beetle is considered a serious threat to beekeeping in the Western Hemisphere, Australia, and Europe, due to larval feeding on honey, pollen, and brood of the honeybee. Release of sterile insects is a possible means to suppress populations in newly invaded areas thus limiting its spread. Irradiation of reproductive adults of both sexes at 45 Gy under low oxygen (1- 4%) caused a high level of sterility (>99%) while maintaining moderate survivorship for several weeks and can be recommended for SIT.

6. Quarantine treatment for fresh apple cultivars. Disinfestation of fresh commodities with X-ray radiation is an effective and accepted quarantine treatment for export markets. ARS scientists in Hilo, Hawaii, collaborated with New Zealand Institute of Plant and Food Research, to determine the tolerance of four apple varieties to ionizing radiation in a commercial facility. All cultivars but ‘Royal Gala’ maintained quality following treatment at doses effective for controlling codling moth and other insect pests. The results will support near-term adoption of x-ray quarantine treatment by the New Zealand apple industry and also future use of this technology by the U.S. apple industry.

U.S. DEPARTMENT OF AGRICULTURE

Tropical Crop and Commodity Protection Research: Hilo, HI