New feasible quarantine disinfestation using ethyl formate for termites and ants on imported lumber

The interception of exotic ants and termites from stone and lumber imported into Korea is on the rise, including Solenopsis invicta. Currently, a relatively long exposure (24 h) of methyl bromide (MB) fumigation is the only practical disinfestation option for exotic ants and termites on imported stone and lumber. In this study, ethyl formate (EF) wase evaluated as a potential MB alternative to disinfest ants and termites in imported lumber, with a focus on S. invicta. As S. invicta is not established in Korea, we first determined whether Reticulitermes speratus, established in Korea, could be considered as an EF surrogate of S. invicta. From 1 h EF fumigation trials, workers of S. invicta were more sensitive to EF than those of R. speratus based on lethal concentration × time causing 99% mortality (LCt_99%), supporting that R. speratus can be used as an EF surrogate of S. invicta. When R. speratus workers were further fumigated with EF for 4 h at four different temperatures, LCt_99% values for R. speratus workers were 108.00, 63.31, 77.24, and 67.24 g h/m³ at 2, 5, 13, and 23 °C, respectively. From scale-up (0.65 m³) and commercial scale (76.4 m³) trials containing two infestation-prone lumber species, lauan (Shorea spp.) and acacia (Acacia spp.), 140 g/m³ EF at >5 °C for 4 h resulted in the complete control of R. speratus workers, suggesting that 140 g/m³ 4 h-EF-fumigation may be applicable as a potential MB-alternative treatment for disinfestation of invasive S. invicta on imported lumber.