Research Project: Postharvest Protection of Tropical Commodities for Improved Market Access and Quarantine Security

Location: Tropical Crop and Commodity Protection Research

2021 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 three broad objectives over the next 5 years: Objective 1: Develop new or improved postharvest treatments or technologies for fresh tropical commodities that mitigate risks associated with quarantine pests and improve quality and shelf-life. • Sub-objective 1A. Develop quarantine irradiation treatments for western flower thrips, tropical nut borer, and the semi-slug Parmarion martensi. • Sub-objective 1B. Evaluate ethyl formate fumigation for thrips control in ornamentals. • Sub-objective 1C. Determine the quality and shelf life of fresh commodities subjected to quarantine irradiation treatment. Objective 2: Develop new preharvest methods for the monitoring and control of phytosanitary and quarantine pests and commodity quality improvement. • Sub-objective 2A. Develop oviposition deterrents for behavioral control of oriental fruit fly and spotted wing drosophila. • Sub-objective 2B. Identify trail pheromone components of little fire ant for improved management in Hawaii. • Sub-objective 2C. Determine preharvest factors that increase aflatoxin prevalence in macadamia nuts. Objective 3: Develop risk management systems and systems approaches to control tropical plant pests and decrease the intensity or need for commodity treatments. • Sub-objective 3A. Evaluate predator breeding stations for augmentative biological control of coffee berry borer in coffee. • Sub-objective 3B. Conduct classical biological control of coffee berry borer using the adult parasitoid Phymasticus coffea. • Sub-objective 3C. Develop a multi-component system for determining chemical and sensory quality associated with coffee berry borer (CBB) damaged coffee and other coffee defects.

Approach
Obj 1A: Quarantine irradiation treatments for western flower thrips, tropical nut borer, and the slug Parnarion martensi will be developed. Dose response data will be generated for mortality, fecundity and fertility. Irradiation treatments will be submitted to USDA APHIS and the IPPC for approval. 1B: Ethyl formate fumigation for postharvest thrips control in ornamentals will be developed, including orchids. Efficacy trials will be conducted with nymph and adult stages using fumigation across concentrations and times. Preliminary data show thrips can be controlled at very low ethyl formate concentrations without loss of orchid quality. 1C: The quality & shelf life of fresh commodities subjected to quarantine irradiation treatment will be determined, particularly for breadfruit. Fresh breadfruit will be irradiated and evaluated for physical, chemical & sensory attributes. If quality is negatively impacted at phytosanitary doses, then combination treatments with hot water or 1-MCP will be tested. Obj 2A: Oviposition deterrents for behavioral control of oriental fruit fly and spotted wing drosophila will be developed. Chemical odors will be extracted from fruits and fungi and screened for attraction or antagonism to fruit flies using field cage tests or GC-EAD & GC-MS analysis. Oviposition deterrents might reduce insecticide spraying. 2B: Trail pheromone components of little fire ant will be identified. Potential candidates will be extracted from venom sac/Dufour’s glands of LFA workers and trails created on epiphytic moss. Bioactivity will be determined via behavioral, chemical and electrophysiological techniques. Pheromones with toxic baits could improve discovery, worker recruitment, and delivery to nests workers. 2C: Preharvest factors increasing aflatoxin in macadamia nuts will be determined. Samples from fields and processor will be evaluated for insect damage & aflatoxins. A prototype in-line fluorescence detector for contaminated nuts will be developed. Aflatoxin detection in immature or insect-damaged nuts can allow mitigation via preharvest insect control, timely harvests, & postharvest sorting. Obj 3A: Predator breeding stations will be evaluated for augmentative biological control of coffee berry borer (CBB) in coffee. Sleeve cages and artificial berries will be used to quantify predation rates in flat bark beetle predators of CBB. Breeding stations will be evaluated for their ability to multiply & augment predators. Increased predators in coffee farms should result in lower CBB populations. 3B: Classical biological control of CBB using the parasitoid Phymasticus coffea will be conducted. P. coffea will be imported from Colombia & tested in quarantine against native and exotic scolytine prey to determine host range. If P. coffea shows no significant nontarget effects, release permits will be obtained. 3C: A system to determine chemical & sensory quality of CBB-damaged coffee will be developed. Methods for volatiles analysis will be developed to distinguish damaged from undamaged beans. If volatile and sensory analyses are effective in differentiating CBB damaged coffee the methodology will be applied to detect other coffee defects.

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 first-year report for the new project 2040-43000-018-00D “Postharvest Protection of Tropical Commodities to Improve Market Access and Quarantine Security”, which replaces the project 2040-43000-017-00D “Pre-and Postharvest Treatment of Tropical Commodities to Improve Quality and Increase Trade Through Quarantine Security.” In support of Sub-objective 1A, phytosanitary irradiation treatments are being developed to support the export of Hawaiian fruits and vegetables to the continental United States. The semi-slug Parmarion martensi is a high priority quarantine pest that occasionally infests exported sweet potatoes and other fruits and is a potential health risk, as it is a primary vector of Angiostrongylus cantonensis, the nematode causing rat lungworm disease in humans. The appearance of P. martensi in Hawaiian exports has raised concerns in California and other export destinations that infected P. martensi may become established there, and that plant inspectors may be exposed and at risk of infection. Irradiation treatment at 150 Gray (Gy) and 400 Gy, the most commonly used generic doses for Hawaii produce and for fruit internationally, prevented any reproduction in P. martensi, suggesting irradiation treatments aimed at disinfestation of quarantine insect pests will also control hitchhiking slugs. Despite the increasing importance of gastropods as quarantine pests, radiotolerance studies are scarce and this is the first report of an irradiation treatment for a slug. In support of Sub-objective 1B, effective fumigation treatments and protocols may help Hawaii ornamental crop growers overcome shipment rejections to the continental United States and abroad due to quarantine restrictions. Thrips cause most of the rejections of cut orchid flowers exported from Hawaii. Initial efficacy data show that one-hour ethyl formate fumigation at a rate of 7.42 gh/m3 at 23°C was effective at controlling western flower thrips and melon thrips. In support of Sub-objective 1C, breadfruit could be exported from the Pacific Basin to high-value markets on the U.S. mainland if an effective phytosanitary treatment was available that did not injure the fruit. Irradiation is more efficient and less phytotoxic than thermal, cold or fumigation treatments. Preliminary trials on the radiation of breadfruit were conducted at 0, 200, 400, 800, and 1000 Gy. To verify differences in chilling injury and radiation damage, we conducted a series of chilling injury experiments at 90% RH at 10, 13, 15, 17, 23°C for up to 15 days postharvest. Breadfruit stored at 10°C had the best postharvest quality. In support of Sub-objective 2A, we isolated and identified a novel repellent compound of spotted wing drosophila from a fermentation product (patent pending). Current control methods to reduce fruit infestation by spotted wing drosophila are based on the constant use of pesticides, which may not be sustainable due to resistance, cost, and negative impact on environment and beneficial insects. When released around raspberries, a preferred host of spotted wing drosophila, the repellent reduced oviposition on fruit by 50% in the field. In support of Sub-objective 2B, research was initiated to identify trail pheromone components of the little fire ant, a nuisance pest that inflicts a painful sting and is spreading to an increasing area of croplands in Hawaii. Adding trail pheromone to little fire ant baits may help recruitment of workers to toxic baits and improve the efficacy of the baits. Chemicals in the Dufour’s gland of the workers of little fire ants were extracted and behaviorally tested for elicitation of trailing behavior. In laboratory bioassays, chemicals in the Dufour’s gland elicited trailing behavior from the workers of little fire ant. In support of Sub-objective 2C, the introduction of Aspergillus fungi through pest-inflicted wounds may result in macadamia kernels with detectable levels of aflatoxin (AF) and market rejection. Analytical methods [high pressure liquid chromatography (HPLC) and a Vicam fluorometer] for measuring aflatoxins in macadamia nuts were developed for the first time and evaluated by measuring field samples from commercial orchards. While the benchtop fluorometer was found to be less accurate and precise in measuring aflatoxins when compared to the HPLC, it was determined to be adequate for measuring field samples at the processor to ascertain the legal threshold of 20 ppm. The HPLC method was able to measure aflatoxins in ranges from 0.15-150 ppm, although field samples never measured above 40 ppm. In support of Sub-objective 3A, predator breeding stations were developed to augment biological control of the coffee berry borer (CBB), the most damaging insect pest of coffee in Hawaii and worldwide. In the field, breeding stations containing cracked corn food and a pheromone lure to attract the predator Cathartus quadricollis were shown to produce an average of 3,000 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. To address Sub-objective 3B, another natural enemy of coffee berry borer, the parasitoid Phymastichus coffea, which attacks CBB adults, was evaluated in quarantine for its host specificity. P. coffea was tested against a wide variety of native and exotic scolytine beetles that occur in Hawaii and appeared to be quite host specific, attacking only Hypothenemus hampei (CBB), its congener the tropical nut borer Hypothenemus obscurus, an exotic pest of macadamia nut, and several other non-pest species of Hypothenemus. There are no Hawaiian native species of Hypothenemus beetles. Therefore, it should be safe to release this parasitoid in Hawaii, with a low risk of any non-target effects or harm to the environment. In support of Sub-objective 3C, coffee producers and processors impacted by infestations of CBB would benefit by knowing what levels of CBB infestation reduce cupping quality and how CBB damage, as well as other defects, affects coffee chemistry. Using automated head-space sampling combined with gas chromatography mass spectroscopy (AHS/GC/MS) and principal component analysis, a method was developed to differentiate undamaged from damaged coffee beans based on volatile profiles. Three compounds associated with undamaged, good quality beans were identified, whereas at least three different compounds were associated with damaged, black, or moldy coffee beans. In-person training of a coffee sensory panel was shifted to virtual sessions due to maximum telework status.

Accomplishments
1. Phytosanitary irradiation treatments control a semi-slug associated with rat lungworm disease in humans. Hawaii island is a hot spot for rat lungworm disease in humans. The primary mode of infection is by accidental ingestion of a plant pest Parmarion martensi, a slug that carries the nematode Angiostrongylus cantonensis which causes the disease, on fresh produce. The slug P. martensi has been found on fresh sweet potatoes and other fruits and vegetables exported from Hawaii to the continental United States that have received phytosanitary irradiation treatment. California and other export destinations are concerned that infected P. martensi may become established there and that plant inspectors may be exposed and at risk of infection. ARS scientists in Hilo, Hawaii, demonstrated that X-ray radiation at 150 and 400 caused reduced feeding, weight gain, and survivorship in P. martensi and prevented reproduction. Phytosanitary irradiation treatment will prevent the establishment of viable populations of P. martensi.

2. A novel oviposition deterrent for spotted wing drosophila. Current control methods to reduce fruit infestation by spotted wing drosophila, a serious invasive pest of cherries and small fruits worldwide, are based on the constant use of pesticides, which may not be sustainable due to resistance, cost, and negative impact on the environment and beneficial insects. A novel oviposition deterrent was identified by ARS researchers in Hilo, Hawaii, that can reduce fruit infestation by spotted wing drosophila by 50%. A patent was filed for the deterrent on February 2021 and a CRADA partner is developing prototype dispensers for on-farm use.

Review Publications
Ban, G., Li, Y., Wall, M.M., Jun, S. 2020. A nanoengineered stainless steel surface to combat bacterial attachment and biofilm formation. Foods. 9(11). Article 1518. https://doi.org/10.3390/foods9111518.
Xu, T., Hansen, L., Cha, D.H., Hao, D., Zhang, L., Teale, S.A. 2020. Identification of a female produced pheromone in a destructive invasive species - Asian longhorn beetle, Anoplophora glabripennis. Journal of Pest Science. 93:1321-1332. https://doi.org/10.1007/s10340-020-01229-3.
Park, M., Park, C., Yang, J., Kim, G., Ren, Y., Lee, B., Cha, D.H. 2020. Ethyl formate as a methyl bromide alternative for phytosanitary disinfestation of imported banana in Korea with logistical considerations. Journal of Economic Entomology. 113(4):1711-1717. https://doi.org/10.1093/jee/toaa088.
Wolfin, M.S., Chilson III, R.R., Thrall, J., Liu, Y., Volo, S., Cha, D.H., Loeb, G.M., Linn Jr, C.E. 2020. Habitat cues synergize to elicit chemically-mediated landing behavior in a specialist phytophagous insect, the grape berry moth. Entomologia Experimentalis et Applicata. 168(12):880-889. https://doi.org/10.1111/eea.13003.
Stockton, D.G., Wallingford, A.K., Cha, D.H., Loeb, G.M. 2020. Automated aerosol puffers effectively deliver 1-octen-3-ol, an oviposition antagonist useful against spotted-wing drosophila. Pest Management Science. 77(1):389-396. https://doi.org/10.1002/ps.6028.
Kwon, T.H., Park, C.G., Lee, B., Zarders, D.R., Roh, G.H., Kendra, P.E., Cha, D.H. 2020. Ethyl formate fumigation and ethyl formate plus cold treatment combination as potential phytosanitary quarantine treatments of Drosophila suzukii in blueberries. Journal of Asia Pacific Entomology. 24(1):129-135. https://doi.org/10.1016/j.aspen.2020.11.008.
Roh, G.H., Cha, D.H., Park, C.G. 2021. Olfactory attraction to aggregation pheromone is mediated by disti-flagellum of antennal segments in Riptortus pedestris. Journal of Asia-Pacific Entomology. 24:415-420. https://doi.org/10.1016/j.aspen.2021.01.005.
Mirshekari, A., Wall, M.M., Madani, B., Biggs, A.R. 2020. Aloe vera coatings maintain antioxidants of fig (Ficus carica L.) fruit during storage. Advances in Horticultural Science. 34(2):205-212. https://doi.org/10.13128/ahsc-8255.
Lee, B.E., You, Y., Choi, W., Hong, E., Wall, M.M., Jun, S. 2020. Nanoengineered superhydrophobic surfaces to prevent the adhesion of Listeria monocytogenes for improved food safety. Transactions of the ASABE. 63(5):1401-1407. https://www.doi.org/10.13031/trans.13934.
Kang, T., You, Y., Hoptowit, R., Wall, M.M., Jun, S. 2021. Effect of an oscillating magnetic field on the inhibition of ice nucleation and its application for supercooling preservation of fresh-cut mango. Journal of Food Engineering. 300. Article 110541. https://doi.org/10.1016/j.jfoodeng.2021.110541.
Laurora, A., Bingham, J., Poojary, M.M., Wall, M.M., Ho, K. 2021. Varietal differences in carotenoid composition and their bioaccessibility from papaya cultivars in Hawaii. Journal of Food Composition and Analysis. 101. Article 103984. https://doi.org/10.1016/j.jfca.2021.103984.
Shankar, S., Follett, P.A., Ayari, S., Hossain, F., Salmieri, S., Lacroix, M. 2020. Microbial radiosensitization using combined treatments of essential oils and irradiation- part B: Comparison between gamma-ray and X-ray at different dose rates. Microbial Pathogenesis. 143. Article 104118. https://doi.org/10.1016/j.micpath.2020.104118.
Follett, P.A., Bruin, J., Desneus, N. 2020. Insects in Agroecosystems - an introduction. Entomologia Experimentalis et Applicata. 168(1):3-6. https://doi.org/10.1111/eea.12871.