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

Location: Tropical Crop and Commodity Protection Research

2025 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 and value-added tropical crops, while protecting U.S. agriculture from pest incursions. This is the final report for the project 2040-43000-018-00D, "Postharvest Protection of Tropical Commodities for Improved Market Access and Quarantine Security", which will be succeeded by a new project titled, "Innovative Crop Protection and Postharvest Systems to Improve Market Access and Product Quality". In support of Sub-objective 1A, ARS researchers in Hilo, Hawaii, developed phytosanitary irradiation treatments to support the export of Hawaii-grown fruits and vegetables to the continental United States. Irradiation treatment at 150 Gy and 400 Gy, the generic doses commonly used for Hawaii produce and for fruit internationally, prevented any reproduction in the semi-slug Parmarion martensi which can infest exported sweet potato tropical fruits. This suggests that irradiation treatments aimed at disinfestation of quarantine insect pests will also control hitchhiking slugs. The 150 Gy dose also deactivated a zoonotic nematode, Angiostrongylus cantonensis, that can infect P. martensi, thus reducing health risks and preventing the spread of the nematode. The western flower thrips, Frankliniella occidentalis, is a major pest of horticultural crops, causing direct damage and transmitting plant diseases, and is a quarantine pest of concern in many countries where it does not occur. Large-scale studies showed that an irradiation dose of 250 Gy could prevent reproduction and thus, irradiation is a phytosanitary treatment option and this dose should be acceptable to the IPPC for use internationally. Under Sub-objective 1B, ARS researchers developed ethyl formate fumigation as a postharvest treatment to reduce shipment rejections of ornamental crop exports from Hawaii to the continental United States due to insects. Thrips cause most of the rejections in exported cut orchid flowers. Dose response tests revealed that one hour ethyl formate fumigation of 7.42 gh/m3 at 23 degrees C was effective at controlling western flower thrips and melon thrips. Ethyl formate fumigation at the specified dose had no noticeable effect on flower color and shelf life. Scale-up confirmatory fumigation trials conducted in fumigation chambers (1 m3) showed complete control of treated thrips without damage on the quality of treated orchids. 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. Radiation is more efficient and less phytotoxic than thermal, cold or fumigation treatments. Three breadfruit varieties were subjected to X-ray radiation at a commercial facility. Fruit ripening and softening were delayed when treated with doses effective for meeting quarantine requirements. Radiated breadfruit maintained postharvest quality in comparison to untreated fruit. Nevertheless, fresh breadfruit has a short shelf-life that is limited by softening and discoloration. Treatment with the ethylene inhibitor, 1-MCP, delayed breadfruit softening, but did not inhibit discoloration. However, breadfruit coated with carnuba wax prior to X-ray treatment retained green color and firmness following treatment and storage at 13C for 10 days, when compared to unwaxed irradiated fruit. This increases the feasibility of exporting fresh breadfruit to distant markets. In support of Sub-objective 2A, ARS researchers identified oviposition deterrents for spotted wing drosophila, oriental fruit fly, and melon fly (a regular U.S. patent application serial no. 18/477,665 was filed under a CRADA). When used as a push component in a push-pull management approach for spotted wing drosophila, spraying the oviposition deterrent on raspberries resulted in significant reduction in spotted wing drosophila oviposition under very high spotted wing drosophila pressure in the field. Progress on Sub-objective 2B, continued research to identify the chemical components of the little fire ant (LFA) trail pheromone and queen pheromone. LFA is a nuisance pest in many agricultural crops in Hawaii that can inflict a painful sting. 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 Dufour’s gland elicited trailing behavior from the workers of little fire ant and increased recruitment of workers. ARS researchers also tested the impact of potential queen pheromone, which may inhibit the development of new queens in the nest. In the laboratory, almost no eggs in colonies with queens became reproductive larvae (that eventually grow to queens), while significantly more LFA eggs in queen-less colonies became reproductive larvae. LFA trail and queen pheromones are being explored for control of LFA. In support of Sub-objective 2C, analytical methods [high pressure liquid chromatography (HPLC) and a Vicam fluorometer] for measuring aflatoxins in macadamia nuts were developed for the first time. Aflatoxins are an emerging problem for the macadamia nut industry. Aflatoxin could be detected using both methods in samples taken directly from commercial orchards, indicating that contamination begins in the orchard. Aflatoxin (AF) was detected at concentrations between 0 and 20 ppb in 15% of samples, and three samples had AF concentrations above 20 ppb. Most (82%) of the samples had no detectable AF. 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 ppb. Insect damage in an orchard location was positively correlated with higher levels of AF. The introduction of Aspergillus fungi through pest-inflicted wounds may result in macadamia kernels with detectable levels of aflatoxin (AF) and market rejection. This research enables macadamia nut producers to identify and reduce the occurrence of contaminated nuts before processing, thereby reducing food safety risks and product rejections. For Sub-objective 3A, ARS researchers developed a predator breeding station consisting of a screened and sheltered enclosure containing food (cracked corn and cornmeal) and a membrane lure with attractants (quadrilure and fungal volatile blend) to augment predator numbers in coffee and macadamia fields. In the laboratory, stocking a breeding station with 100 C. quadricollis resulted in production of about 10,000 adults per station over a four-month period at 25 degrees C, demonstrating the station’s potential for multiplying predators in the field. The predator breeding station is being used to augment biological control of the coffee berry borer on several large coffee farms and is being explored similarly for control of tropical nut borer in macadamia nut orchards. In support of Sub-objective 3B, after host specificity testing, environmental and cultural impact assessments were submitted to regulatory authorities for approval for the release of Phymasticus coffea, a parasitoid of the adult coffee berry borer (CBB). P. coffea, originally from Africa, has been introduced against CBB in many coffee-producing countries. The request for field release of P. coffea in Hawaii was approved and permits were received. A requirement upon import of the parasitoid is to rear it for two generations under quarantine containment conditions to ensure there are no hyperparasitoids or other contaminants. The first field release in coffee fields is anticipated for late 2025. In support of Sub-objective 3C, damage to coffee during growing, processing or roasting can change the volatile chemicals or flavors produced in the beverage. Dynamic headspace sampling (HS) coupled to gas chromatography/mass spectrometry (GC-MS) was compared with an electronic nose (e-nose) to investigate changes in the volatile profiles of multiple defects in green and roasted coffee. Volatile and sensory analyses were effective in differentiating coffee berry borer (CBB) damaged green coffee from undamaged beans, and the methodology was applied to detect other coffee defects in roasted coffee beans. Overall, for green and roasted coffee beans, analyses performed using HS/GC/MS were better able to differentiate between the tested coffee samples than the e-nose. A sensory panel, trained to evaluate specialty coffee flavor and aroma, was also able to identify and differentiate off-flavors and aromas of multiple coffee defects in roasted samples, including CBB damage. In other research, near-infrared (NIR) spectroscopy was developed to discriminate gamma irradiated vs. non-irradiated Medfly so that SIT sterile release flies could be separated from wild flies in traps in the field. NIR classification systems are also being developed to determine navel orangeworm (NOW) dietary experiences, to separate two bark beetle pests tropical nut borer and coffee berry borer, to distinguish between Hawaii’s common commercial avocado cultivars, and to separate diseased from healthy macadamia nut saplings. Nanoscale cinnamaldehyde in ß-CD inclusion complexes (fruit coatings) were shown to preserve the shelf life of rambutan by retarding peel browning and inhibiting microbial growth. Field studies confirmed the effectiveness of verbenone and methyl salicylate as repellents against the macadamia pest tropical nut borer. Mating disruption (MD) in a commercial macadamia orchard resulted in reduced egg laying and nut injury by Cryptophlebia moths.

Accomplishments
1. Lisbon lemons cleared for export from Hawaii. Citrus spp. grown in Hawaii cannot be exported to the continental United States without a quarantine treatment or other mitigation measures to control possible infestations by Oriental fruit fly, Mediterranean fruit fly, and melon fly. A farm on the island of Maui, Mahi Pono, is harvesting 1,000 ha of Lisbon lemons and may soon exceed local markets for fruit, therefore, an export option was needed. ARS scientists in Hilo, Hawaii, used laboratory and field cage tests and large-scale collection of fruit from the field to show that Lisbon lemon is a non-host for all three fruit flies. Lemons could be safely exported from Hawaii to the continental United States or Pacific Rim countries without a quarantine treatment.

2. Quarantine treatment for fresh breadfruit. Disinfestation of fresh commodities with X-ray radiation is an effective and accepted quarantine treatment for export markets. Fresh breadfruit are hosts to quarantine pests such as tephritid fruit flies. 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. Fresh breadfruit also has a short shelf-life that is limited by softening and discoloration. ARS scientists in Hilo, Hawaii, determined the quality of fresh breadfruit following coating with carnauba wax and treatment with ionizing radiation at doses suitable for disinfestation of quarantine pests. Breadfruit coated with carnuba wax prior to X-ray treatment retained green color and firmness, thereby extending shelf-life. Wax coating combined with radiation treatment of breadfruit at doses less than 800 Gy ensured marketable quality while providing quarantine security for breadfruit exports.

3. Volatile analysis for coffee quality. Coffee beans can be damaged during growing, processing, and roasting, which can reduce coffee quality and price. Coffee damage often results in changes to the volatile chemicals or flavors produced by coffee. ARS scientists in Hilo, Hawaii, developed gas chromatography/mass spectrometry (GC-MS) and electronic nose (e-nose) methods to characterize the volatile profiles associated with multiple defects in green and roasted coffee, including coffee berry borer damage. Volatile and sensory analyses were effective in differentiating coffee berry borer (CBB) damaged green coffee from undamaged beans, and the methodology was applied to detect other coffee defects (black, chipped, moldy, tan) in roasted coffee beans. Analysis of coffee volatiles is an effective, objective method of assessing the flavor quality of coffee, beyond visual indicators of damage, and could replace taste tests used by industry.

Review Publications
Reay-Jones, F.P., Schnabel, G., Bryant, T.B., LaForest, J., Melanson, R.A., Acebes-Doria, A.L., Blaauw, B. 2025. MyIPM smartphone applications—Tools to increase adoption of integrated pest management. Journal of Integrated Pest Management. 16(1). Article 3. https://doi.org/10.1093/jipm/pmae038.
Shu, C., Yusufali, Z., Ho, K.K.H.Y., Sun, X.N. 2025. Nanoencapsulated cinnamaldehyde@ß-cyclodextrin inclusion complexes as a sustained release strategy for postharvest rambutan preservation. Food Hydrocolloids. 159. Article 110724. https://doi.org/10.1016/j.foodhyd.2024.110724.
Joya, A., Lee, D., Kang, T., Wall, M.M., Jun, S. 2025. Effect of oscillating magnetic field (OMF) on the supercooling behavior of iron-oxide nanoparticle (IONP) agar model system. Journal of Food Science. 90(1). Article e17653. https://doi.org/10.1111/1750-3841.17653.
Follett, P.A., Sun, X.N., Walse, S.S. 2024. Host status of Persian lime (Citrus latifolia Tan.) to oriental fruit fly and Mediterranean fruit fly (Diptera: Tephritidae) in Hawai’i. Insects. 15(10). Article 799. https://doi.org/10.3390/insects15100799.
Acebes-Doria, A.L., Aigbedion-Atalor, P. 2025. Exploiting trap type and color for monitoring macadamia felted coccid Acanthococcus ironsidei (Williams) and associated parasitic wasps in macadamia orchards in Hawai’i. Insects. 16(2). Article 149. https://doi.org/10.3390/insects16020149.
Follett, P.A., Sun, X.N., Walse, S.S. 2025. Non-host status of green lemon fruit (Citrus x limon (L.) Burman f. cv. Lisbon) to Oriental fruit fly, Mediterranean fruit fly, and melon fly (Diptera: Tephritidae) in Hawaii. Insects. 16(5). Article 447. https://doi.org/10.3390/insects16050447.
Nixon, L.J., Acebes-Doria, A.L., Kirkpatrick, D., Leskey, T.C. 2024. Influence of deployment method and maintenance on efficacy of sticky card traps for Halyomorpha halys (Hemiptera: Pentatomidae). Journal of Economic Entomology. 117(5):2003-2008. https://doi.org/10.1093/jee/toae192.
Shrestha, B., Hesler, S.P., Meier, L., Cha, D.H., Loeb, G.M. 2024. Field testing of 2-pentylfuran as a behavioural control tool for spotted-wing drosophila in raspberries. Journal of Applied Entomology. 149(2):248-255. https://doi.org/10.1111/jen.13366.
Roy, K., Mikros, D.S., Cha, D.H., Dunkle, E.J., Juzwik, J., Ginzel, M. 2024. The efficacy of the semiochemical repellent verbenone to reduce ambrosia beetle attack on healthy and Ceratocystis-infested ‘ohi'a trees. Forests, Trees and People. 18. Article 100735. https://doi.org/10.1016/j.tfp.2024.100735.
Movva, V., Zhu, J.J., Roda, A., Kendra, P.E., Yang, X., Cloonan, K.R., Tay, J., Cha, D.H. 2024. Deterrence and behavioral mode of coconut oil-derived free fatty acids on Zeugodacus cucurbitae oviposition. Insect Science. https://doi.org/10.1111/1744-7917.13460.
Follett, P.A., Fezza, T.J., Ladizinsky, N.C., Liang, P. 2024. Comparing the biological effectiveness of low energy 100 kV and high energy 5 MeV X-rays against Oriental fruit fly (Diptera: Tephritidae). Journal of Economic Entomology. 117(5):1815-1822. https://doi.org/10.1093/jee/toae169.
Roy, K., Brill, E., Mikros, D., Tobin, K., Juzwik, J., Mcnellis, B.E., Jacobs, D., Keith, L.M., Cha, D.H., Ginzel, M. 2025. The in vitro and in vivo fungal volatile organic compounds associated with rapid 'Ohi'a death and the response of Xyleborine ambrosia beetles to those compounds. Journal of Chemical Ecology. 51. Article 59. https://doi.org/10.1007/s10886-025-01606-1.
Movva, V., Shrestha, B., Hesler, S.P., Sun, X.N., Zhu, J.J., Loeb, G.M., Tay, J., Cha, D.H. 2025. Oviposition deterrent as a component of a push-pull management approach for Drosophila suzukii. Environmental Entomology. Article nvaf057. https://doi.org/10.1093/ee/nvaf057.
Kim, D., Kim, K., Kwon, T., Cha, D.H., Lee, B. 2025. Ethyl formate fumigation and nematicidal dip treatments as methyl bromide alternative treatments for the longtailed mealybug (Pseudococcus longispinus) and the root-lesion nematode (Pratylenchus penetrans) on imported nursery plants. Journal of Economic Entomology. Article toaf092. https://doi.org/10.1093/jee/toaf092.