Postharvest control of western flower thrips (Thysanoptera: Thripidae) and California red scale (Hemiptera: Diaspididae) with ethyl formate and its impact on citrus fruit quality

Ethyl Formate Fumigation for Controlling Two Major Aphid Pests, Aphis spiraecola and Aphis gossypii, on Passion Fruit, from Cultivation to Post-Harvest Storage

Tropical and subtropical crops are being increasingly cultivated in South Korea, leading to an increase in damage by exotic insect pests. Consequently, ethyl formate (EF) is currently being considered for quarantine and pre-shipment fumigation. In this study, we evaluated the effectiveness of EF fumigation for controlling Aphis spiraecola Patch and Aphis gossypii Glover, two representative quarantine pests on passion fruit ("Pink Bourbon") during greenhouse cultivation and post-harvest storage. The efficacy of EF against both aphids in terms of the lethal concentration causing 50% mortality (LCt50%) and LCt99% was 1.36-2.61 g h/m3 and 3.73-7.55 g h/m3 under greenhouse conditions (23 °C), and 1.37-2.02 g h/m3 and 3.80-14.59 g h/m3 post-harvest (5 °C), respectively. EF at 4 g/m3 for 4 h resulted in 100% mortality of A. spiraecola, which was more resistant to EF, without causing phytotoxic damage to the trees in a 340 m3 greenhouse. Post-harvest fruit fumigation at 10 g/m3 for 4 h in a mid-size (0.8 m3) fumigation chamber resulted in complete disinfection. Moreover, the EF level decreased below the EF threshold within 10 min after natural ventilation in the greenhouse. Therefore, our results suggest EF fumigation as an effective method for controlling A. spiraecola and A. gossypii.

Ethyl Formate Fumigation against Pineapple Mealybug, Dysmicoccus brevipes, a Quarantine Insect Pest of Pineapples

Pineapple mealybug, Dysmicoccus brevipes (Hemiptera: Pseudococcidae), is a significant pest in pineapple production and a key trade barrier. We explored the potential use of ethyl formate (EF) as a methyl bromide alternative for the postharvest fumigation of D. brevipes in imported pineapples. When treated at 8 °C for 4 h, EF fumigation was effective against D. brevipes with LCt99, the lethal concentration × time product of EF necessary to achieve 99% mortality of D. brevipes nymphs and adults at 64.2 and 134.8 g h/m3, respectively. Sorption trials conducted with 70 g/m3 EF for 4 h at 8 °C using 7.5, 15 and 30% pineapple loading ratios (w/v) indicated that loading ratio lower than 30% is necessary to achieve the LCt99 values required to control D. brevipes. In a scaled up trial using 1 m3 chamber, EF fumigation with 70 g/m3 for 4 h at 8 °C with 20% pineapple loading ratio (w/v) resulted in a complete control of D. brevipes treated. There were no significant differences in hue values, sugar contents, firmness, and weight loss between EF-treated and untreated pineapples. Our results suggest that EF is a promising alternative to methyl bromide fumigation for the postharvest phytosanitary disinfection of D. brevipes in pineapples.

A Novel Ethyl Formate Fumigation Strategy for Managing Yellow Tea Thrips (Scirtothrips dorsalis) in Greenhouse Cultivated Mangoes and Post-Harvest Fruits

The effects of climate change and shifting consumer preferences for tropical/subtropical mango fruits have accelerated their greenhouse cultivation in South Korea, which has consequently exacerbated the risk of unexpected or exotic insect pest outbreaks. This study used the pest risk analysis (PRA) of greenhouse-cultivated mangoes provided by the Animal & Plant Quarantine Agency in Korea to evaluate the potential of ethyl formate (EF) fumigation as a new pest management strategy against the yellow tea thrips (Scirtothrips dorsalis), which is considered a surrogate pest in the thrips group according to the PRA. The efficacy and phytotoxicity of EF were evaluated in greenhouse-cultivated mango tree (Irwin variety) and post-harvest mango fruit scenarios. EF efficacy ranged from 6.25 to 6.89 g∙h/m³ for lethal concentration time (LCt)₅₀ and from 17.10 to 18.18 g∙h/m³ for LCt₉₉, indicating similar efficacy across both scenarios. Application of 10 g/m³ EF for 4 h at 23 °C could effectively control S. dorsalis (100% mortality) without causing phytotoxic damage to the greenhouse-cultivated mango trees, while post-harvest mango fruit fumigation with 15 g/m³ EF for 4 h at 10 °C showed potential for complete disinfestation of S. dorsalis without compromising fruit quality.

Fumigant Activity of Ethyl Formate against the Chestnut Weevil, Curculio sikkimensis Heller

Simple Summary

Fumigation is the most effective method for the control of Curculio sikkimensis in chestnuts. The effects of ethyl formate (EF) as a fumigant were investigated to evaluate its potential for practical use by farmers. A dose of 180.0 g/m³ and 12 h of fumigation resulted in 100% mortality on a small scale (2 m³). The results of these experiments indicate that EF could be conveniently used as a fumigant by farmers.

Abstract

Castanea crenata Siebold & Zucc. (Fagales: Fagaceae), a species of chestnut native to Korea and Japan, is distributed in Korea, Japan, and northeastern China, where chestnuts are a major economic agroforest product. Curculio spp. is among the main known pests of chestnuts around the world. In Korea, only phosphine (PH₃) is permitted for the fumigation of C. sikkimensis larva-infested chestnuts. However, it is applied for large-scale fumigation, and its use is restricted. Moreover, it requires a long exposure time and an application device; thus, it cannot be used by small-scale farmers. In this study, the activity of ethyl formate (EF) as a fumigant against Curculio sikkimensis in chestnuts was investigated, and its potential for practical use by farmers was evaluated. The sorption of EF according to the filling ratio (FR) and fumigation time was tested, and the results revealed that 2.5% FR was the most effective. For C. sikkimensis in chestnuts, the mortality rate increased proportionately with the dose of EF. After exposure to 160 g/m³ of EF in a 12 L desiccator, the adult C. sikkimensis showed 100% mortality. According to the time–dose mortality data collected over 12 h of fumigation, the LCT₉₀ and LCT₉₉ values were estimated as 1052.0 and 1952.0 g·h/m³. The results revealed that immersion was not an effective method for controlling C. sikkimensis. According to the LCT values, a dose of 180.0 g/m³ and 12 h of fumigation resulted in 100% mortality on a small scale (2 m³). The results of this experiment indicate that EF could be conveniently used as a fumigant by farmers.

Ethyl Formate as a Methyl Bromide Alternative for Fumigation of Citrus: Efficacy, Fruit Quality, and Workplace Safety

Ethyl formate (EF) was evaluated as a potential alternative to methyl bromide (MB) for phytosanitary treatment of imported citrus fruit in the Republic of Korea. Planococcus citri (Risso) (Hemiptera: Pseudococcidae), a mealybug with known tolerance against EF and MB, was used as a representative pest to test efficacy of the two fumigants against eggs. In nine commercial-scale refrigerated container (67.5 m3) trials using imported orange, lemon and grapefruit, EF applied at the currently approved dose for citrus (70 g·m-3 at 5°C for 4 h, developed for Aspidiotus excisus Green (Hemiptera: Diaspididae), a species less EF tolerant than P. citri) resulted in 76.9-98.3% mortality of P. citri eggs. The EF treatment did not affect the sugar content or the color of peel and pulp of the treated fruit. When oranges were treated according to the current MB (64 g·m-3 at >5°C for 2 h) or EF treatment guidelines, the concentration of fumigant around the fruit fluctuated between 9.4 and 185.1 ppm for EF and 9.5-203.0 ppm for MB during the 72-h post-fumigation processes (venting [0-2 h], transportation to storage [2-24 h], and storage periods [24-72 h]) with both EF and MB maintained between 10 and 100 ppm during the storage period. Considering the efficacy of EF, its apparent lack of phytotoxicity, and its more manageable threshold limit value for humans (100 ppm EF compared to 1 ppm MB for an 8-h time weighted average exposure), our results suggest that EF may be a promising alternative to MB for the phytosanitary treatment of imported citrus in Korea.

Ethyl Formate as a Methyl Bromide Alternative for Phytosanitary Disinfestation of Imported Banana in Korea With Logistical Considerations

Methyl bromide (MB) use for quarantine and phytosanitary purposes is being phased out. Several effective MB alternatives have been identified depending on the target system. Industry commitment for the shift to new technologies will depend not only on the efficacy of alternatives but also on their compatibility and integrability into existing operations. We compared the efficacy of MB and ethyl formate (EF) for disinfestation of Planococcus citri (Risso) (Hemiptera: Pseudococcidae) as a representative surface pest on banana and evaluated whether EF fumigation is compatible with the current packaging materials and loading ratio used by the South Korean banana import industry. Fumigation trials with P. citri adults and eggs showed that EF was at least as effective as MB at the EF and MB concentrations recommended under the current phytosanitary disinfestation guidelines. From a logistical standpoint, EF gas could not effectively penetrate plastic bagging typically used in banana cartons during commercial shipping. Also, EF sorption to bananas and packing materials (used as cushioning inside bagging) further lowered realized EF concentrations around bananas. These reductions in EF concentration translated into reduced mortality of P. citri eggs, indicating that despite similar efficacy of MB and EF for controlling P. citri, further consideration and optimization of other industry logistics such as packaging and loading ratio is necessary to enhance the adoption of this MB alternative.

Use of Ethyl Formate Fumigation to Control Adult Bean Thrips in Navel Oranges

Shipments of California Navel oranges (Citrus sinensis) (Osbeck)) that are found to be infested with adult bean thrips (Caliothrips fasciatus (Pergande) (Thysanoptera: Thripidae)) upon arrival in Australia either undergo mandatory fumigation with methyl bromide (MeBr) to kill the thrips or are refused entry. Ethyl formate (EtF) mixed with carbon dioxide (CO₂) is an effective fumigant for control of various arthropods including but not limited to, thrips, aphids, Pacific spider mites, California red scale, and omnivorous leaf rollers. Dose-mortality curves at 5°C, 10°C, and 15°C were developed for control of adult bean thrips using EtF plus CO₂, with 5°C being more effective. In further testing, the efficacy of EtF plus CO₂ against adult bean thrips in Navel oranges and the impact on fruit quality after fumigation followed by 5 wk of storage at 5°C and shelf life at 20°C was determined. Fruit fumigated with 31 g/m3 EtF plus CO₂ at 5°C for 1 h showed no difference in quality compared with untreated control fruit. Ethyl formate plus CO₂ fumigation efficacy was confirmed in a 27.32 m3 sea freight container with eight pallets of packed Navel oranges (load factor 28.69%) and 10,000-15,000 adult bean thrips in each of three replications. Complete control of adult bean thrips was achieved with no negative effects on fruit quality.

Tuning the Composition of Electrodeposited Bimetallic Tin-Lead Catalysts for Enhanced Activity and Durability in Carbon Dioxide Electroreduction to Formate

Bimetallic Sn-Pb catalysts with five different Sn/Pb atomic ratios were electrodeposited on Teflonated carbon paper and non-Teflonated carbon cloth using both fluoroborate- and oxide-containing deposition media to produce catalysts for the electrochemical reduction of CO₂ (ERC) to formate (HCOO^- ). The interaction between catalyst composition, morphology, substrate, and deposition media was investigated by using cyclic voltammetry and constant potential electrolysis at -2.0 V versus Ag/AgCl for 2 h in 0.5 m KHCO₃ . The catalysts were analyzed before and after electrolysis by using SEM and XRD to determine the mechanisms of Faradaic efficiency loss and degradation. Catalysts that are mainly Sn with 15-35 at % Pb generated Faradaic efficiencies up to 95 % with a stable performance. However, pure Sn catalysts showed high initial stage formate production rates but experienced an extensive (up to 30 %) decrease of the Faradaic efficiency. The XRD results demonstrated the presence of polycrystalline SnO₂ after electrolysis using Sn-Pb catalysts with 35 at % Pb and its absence in the case of pure Sn. It is proposed that the presence of Pb (15-35 at %) in mainly Sn catalysts stabilized SnO₂ , which is responsible for the enhanced Faradaic efficiency and catalytic durability in the ERC.

Eliminating Macchiademus diplopterus (Hemiptera: Lygaeidae) and Siculobata sicula (Acari: Oribatulidae) From Export Fruit Using Ethyl Formate

South African fruit is sometimes rejected for export for the presence of live arthropods that are not considered pests of the fruit concerned. Macchiademus diplopterus (Distant) (Hemiptera: Lygaeidae) is a cereal pest but may aestivate on fruit of some tree crops in the Western Cape province of South Africa and occasionally results in rejections of export fruit. Ethyl formate in the form of the commercial product Vapormate (a patented combination of ethyl formate and carbon dioxide) was evaluated as a fumigant against M. diplopterus at a dosage of Vapormate 250 g/m3 or ethyl formate 1.29% and carbon dioxide 10.76% (both by volume) and when applied for 4 h gave complete control. Confirmatory trials with >35,000 M. diplopterus using the same treatment, resulted in no survivors. The arboreal mite Siculobata sicula (Berlese) (Sarcoptiformes: Oribatulidae) at times reaches high numbers on citrus in orchards if few pesticides are used and may result in export rejections. A small-scale trial using the same ethyl formate treatment also killed these mites. This treatment-time combination did not appear to have phytotoxic effects on pears or oranges, unless they had prior mechanical injuries that were accentuated. Ethyl formate therefore holds promise for disinfesting fruit before it is packed.