Effectiveness of Ethyl Formate as a Fumigant of Blattella germanica and Periplaneta americana (Blattodea: Ectobiidae, Blattidae) in Cross-Border Trade Transportation.

Cockroaches cause problems as pests not only locally in residential areas but also internationally, as they can disperse across borders in transport vessels. We investigated the effects of the ethyl formate (EF) fumigant on all developmental stages of Blattella germanica and Periplaneta americana. For B. germanica eggs, the hatching inhibition rate increased directly proportionately with the increasing treatment concentration of EF, but the 100% control was not observed. P. americana eggs did not show any fumigation effect, even after exposure to 60 mg/L of fumigant in a 12 L desiccator. Adults and nymphs of the two species showed various fumigation effects dependent on the concentration in the 12 L desiccator. When EF was applied at the lethal concentration for 99% mortality (LCT99) values of 35 mg/L for 4 h (78.5 mg·h/L) and 60 mg/L for 2 h (70.8 mg·h/L), respectively, adults and nymphs of both species had 100% mortality in a 0.65 m3 fumigation chamber with a 20% loading ratio. However, no significant difference from the control was observed in the egg stage of either species of cockroach. The results of this experiment indicate that EF can be used as a fumigant for cross-border transport vessels if the control period occurs during the cockroach developmental stage and continuous refumigation is performed.

Comparison of the Efficacy and Phytotoxicity of Phosphine and Ethyl Formate for Controlling Pseudococcus longispinus (Hemiptera: Pseudococcidae) and Pseudococcus orchidicola on Imported Foliage Nursery Plants.

The fumigation activity of phosphine (PH3) and ethyl formate (EF) and their phytotoxicity to 13 imported foliage nursery plant species were evaluated. The lethal concentration and time (LCT99) values of the PH3 indicated that the susceptibility of the nymphs (3.95 and <0.45 mg·h/liter, respectively) was higher than that of the adults (5.29 and 3.66 mg·h/liter, respectively) of two mealybugs [Pseudococcus longispinus (Targioni-Tozzetti) and P. orchidicola Takahashi]. The highest concentration reduction rate of PH3 and EF on the 13 foliage nursery plants in the 12-liter desiccator was 41.5% for Heteropanax fragrans and 71.7% for Schefflera arboricola, respectively, which indicates that PH3 has a lower sorption rate than EF. The phytotoxicities of PH3-treated foliage nursery plants did not significantly differ from those of the nontreated plants, but EF caused phytotoxicity in 11 foliage nursery plants a week after treatment. When the exposure time of PH3 increased to 24 h, the adults and nymphs of both mealybug species showed 100% mortality in the 0.5 m3 fumigation chamber. In the 10 m3 fumigation container used in the field, there was 100% mortality of both mealybugs after treatment with 2 g/m3 PH3 for 24 h at 16°C. These results indicate that EF is not a suitable mealybug fumigant due to its high sorption and phytotoxicity to foliage nursery plants, despite fumigation activity against the two species. However, PH3 seems to be suitable for mealybug fumigation in foliage nursery plants and can be used as a substitute for methyl bromide.

Efficacy and Phytotoxicity of Phosphine as Fumigants for Frankliniella occidentalis (Thysanoptera: Thripidae) on Asparagus.

The insecticidal activity of phosphine (PH3) and ethyl formate (EF) toward Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) and their phytotoxicity to asparagus were evaluated. Both the PH3 and EF fumigants showed higher lethal concentration and time (LCT) values at lower temperatures. The LCT99 values of PH3 and EF at 5°C in a 12 liters desiccator for 4 h showed the following ranking: eggs (64.69 mg·h/liter for PH3 and EF indicating phytotoxicity to asparagus), nymphs (5.54 and 17.48 mg·h/liter, respectively), and adults (3.83 and 14.67 mg·h/liter, respectively). The adsorption of PH3 was approximately 11% at 2°C and 13% at 5°C, whereas the adsorption of EF increased sharply to 88% at 2°C and 97% at 5°C. The hatching rate of F. occidentalis eggs was approximately 95% at all locations (top, middle, and bottom) in the presence of 4 mg/liter PH3 at 5°C in a 0.65-m3 fumigation chamber for 24 h. However, extension of the treatment to 48 h resulted in 100% inhibition of egg hatching. The atmospheric level of PH3 decreased below the threshold limit value after 80 min, and phytotoxicity was not observed. The results revealed that EF is highly absorbed by asparagus and is not suitable as a fumigant, but PH3 is a suitable alternative to the fumigant methyl bromide for the control of western flower thrips in asparagus.

Fumigation Activity of Ethyl Formate and Phosphine Against Tetranychus urticae (Acari: Tetranychidae) on Imported Sweet Pumpkin.

This study investigated an alternative fumigant for imported sweet pumpkin. Laboratory fumigations with ethyl formate (EF) and phosphine (PH3) alone and in combination were conducted at different temperatures in 12-liter desiccators to determine their efficacy and synergism against adults and eggs of two-spotted spider mites (Tetranychus urticae Koch), a major pest of sweet pumpkins; larger scale fumigations with EF were also performed to evaluate the impact of EF fumigation on the postharvest quality of sweet pumpkin and EF absorption. EF fumigation of 4 h achieved 100% control of both adults and eggs at 10°C. Efficacy of EF also increased with temperature. Conversely, PH3 fumigation for 4 and 6 h was not effective against either adults or eggs, and no synergism between EF and PH3 was observed. In larger scale fumigation tests, EF at 60 g/m3 for 4 h resulted in 100% control of both adults and eggs at 10°C, without causing injury to the sweet pumpkins. These results suggest that EF has the potential to be a safe and effective alternative to methyl bromide fumigation for controlling two-spotted spider mites on sweet pumpkin.