This study was conducted to evaluate the insecticidal effects of ethyl formate (EF), methyl bromide (MB), and phosphine (PH₃) fumigants against PH₃-susceptible and -resistant strains of the rice weevil (Sitophilus oryzae), a major rice pest. The highest lethal concentration time 50 (LCt₅₀) values of the PH₃-susceptible strains were 255.797, 21.104, and 6.171 mg h L⁻¹ for EF, MB, and PH₃, respectively, at pupal stage. The highest LCt₅₀ values of the PH₃-resistant strains were 149.028 and 48.170 mg h L⁻¹ for EF and PH₃, respectively, at late larval stage, and 43.520 mg h L⁻¹ for MB at pupal stage. In comparison to the susceptible strains, the PH₃-resistant strain collected in South Korea had a resistance level 4 to 56 times higher. Use of the major quarantine fumigants EF, MB, and PH₃ indicated the existence of PH₃-resistant rice weevils in South Korea for the first time.

Quarantine treatments by phosphine (PH₃) gas have been performed to replace methyl bromide (MeBr) for export cut flowers and imported nursery plant in Korea. In this preliminary study, two dominant insect pests of cut flowers, Tetranychus urticae Koch and Frankliniella occidentalis Pergande, and the dominant insect pest of nursery plants, Planococcus citri Risso, were used to certify optimum concentration and fumigation time, along with evaluation of phytotoxic damages. To validate the results of preliminary tests, quarantine treatments for export cut flowers was performed in a 58-m³ reefer container. When 14 species of cut flowers were fumigated with 2 g m⁻³ PH₃ for 24 h (Ct product was 30.9 g h m⁻³) at 5 °C, all pests were effectively controlled and no phytotoxic damage were observed on roses and chrysanthemums. On quarantine trials for imported nursery trees, which was performed at 10 m³ scale covered with a PVC-tarpaulin tent, 2 g m⁻³ of PH₃ for 24 h (Ct product was 30.0 g h m⁻³) at 15 °C was enough to kill all pests and no damage was observed on seven species of nursery plants. Phosphine gas shows the promise as MeBr alternative to perishable commodities in terms of efficacy to certain quarantine pest and maintenance of its quality as well as being a more environmentally safe fumigant.

The susceptibility of Lasioderma serricorne to phosphine (PH₃), ethyl formate (EF) and their combination (PH₃ + EF) was evaluated in this study. Eggs, larvae, pupae and adults were subjected to treatment with fumigants to determine the 90% lethal concentration time (LCt₉₀) values. Treatment with PH₃ for 20 h resulted in LCt₉₀ values of 1.15, 1.39, 14.97 and 1.78 mg h/L while treatment with EF resulted in values of 157.96, 187.75, 126.06 and 83.10 mg h/L, respectively. By contrast, the combination of PH₃ + EF resulted in LCt₉₀ values of 36.05, 44.41, 187.17 and 35.12 mg h/L after 4 h. These results show that, through treatment with PH₃ + EF, control can be achieved at lower concentrations than for treatment with EF alone and at lower exposure times than for treatment with PH₃ alone. The sorption rates of the fumigants on cured tobacco leaves were determined for filling ratios of 2.5%, 5.0% and 10.0% (w/v). Cured tobacco leaves were treated with either 2 mg/L PH₃, 114 mg/L EF or 0.5 mg/L PH₃ + 109 mg/L EF. Treatment with PH₃ showed sorption rates of 0.0%, 7.1% and 14.3%. EF, however, showed higher sorption rates of 64.9%, 68.5% and 75.5%, respectively, for the indicated filling ratios. When PH₃ and EF were combined, the sorption rate of PH₃ was 0.0%, while the sorption rates of EF were lower (9.1%, 12.0% and 23.2%) than treatment with only EF. EF required a ventilation time of longer than 22 h to desorb from cured tobacco leaves. Therefore, PH₃ + EF can effectively control L. serricorne in cured tobacco leaves, with sufficient ventilation time required after treatment for the safety of workers.

Drosophila suzukii is a quarantine pest that is rapidly spreading in berries. This study evaluated the synergistic effect of combination treatment with ethyl formate (EF) and cold temperature for D. suzukii control on imported grapes. A higher insecticidal effect was observed at 1 °C than at 5 °C at all developmental stages, and the pupal stage showed the strongest tolerance to cold temperature. After EF fumigation alone, eggs showed the highest tolerance at 216.67 mg·h/L (LCT₉₉ value), and adults showed the highest susceptibility at <27.24 mg·h/L. Among the combination treatment methods, cold temperature after fumigation resulted in the best synergistic effect. The effect of this combination was significant, with 23.3% higher mortality for eggs, 22.4% for larvae, and 23.4% for pupae than observed with EF fumigation alone. Furthermore, the period of complete D. suzukii control in the 12 L desiccator was shorter in the combination treatment group at the LCT₈₀ value than at the LCT₅₀ value of the egg stage. EF showed a very high sorption rate (24%) after 4 h of exposure at a grape loading ratio of 15% in a 0.65 m³ fumigation chamber. As the grape loading ratio for combination treatment decreased, D. suzukii mortality increased, but when EF was administered at the LCT₈₀ value, there was little difference in the mortalities of the eggs and larvae but not the pupae. All D. suzukii developmental stages were completely controlled within 7 days after combination treatment, and phytotoxicity was not observed in grapes. These results suggest that the combination of cold-temperature treatment and EF fumigation could be used for D. suzukii control.

Phosphine resistance is occurring among stored-grain pests worldwide. This study investigated the fumigation activity of phosphine (PH₃) and carbonyl sulfide (COS) against domestic strain (d-strain) Tribolium castaneum, resistance strain (r-strain) T. castaneum and Oryzaephilus surinamensis. All developmental stages of the pests were exposed to two fumigants (PH₃ and COS), and the fumigation activity according to the dose and exposure time was evaluated in a 12-L desiccator and 0.5 m³ fumigation chamber. The rice sorption rate and quality following exposure to thetwofumigants were evaluated. The mortality was 2.9% in r-strain T. castaneum, 49.5% in d-strain T. castaneum and 99.2% in O. surinamensis when 2 mg/L PH₃ was used in a 12-L desiccator for 4 h. However, all pest developmental stages showed 100% mortality after 24 h of exposure in the 0.5 m³ fumigation chamber, except for the r-strain T. castaneum. A mortalityof 100% was observed in all of the r-strain T. castaneum developmental stages at an exposure time of 192 h. For COS applied at 40.23 mg/L and 50 g/m³ in the 12-L desiccator and the 0.5 m³ fumigation chamber, respectively, 100% mortality was observed across all developmental stages regardless of species and strain. The sorption of COS was 10% higher than that of PH₃, but there was no significant difference in rice quality compared to that in the control. Therefore, this study suggests that COS can be used for controlling T. castaneum resistant to PH₃.

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 LCt_99, 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.