Fumigant toxicity of phosphine to the Japanese termite, Reticulitermes speratus Kolbe (Isoptera: Rhinotermitidae)

Phosphine (PH3) gas is a quarantine fumigant for stored products and an alternative to methyl bromide (MB). PH3 was tested for its fumigant toxicity to the Japanese termite, Reticulitermes speratus. Its permeability and sorption to two different materials (wood and petri dish) were also tested. Termites were exposed to PH3 under different conditions of temperature and wood moisture content. The fumigant toxicities of PH3 (LCT50 values) to termites were 0.735 mg h/L and 0.744 mg h/L at 20 °C in wood and petri dishes, respectively. Fumigant activity was approximately 8 times higher at 15 °C than that at 5 °C. There was no significant difference between the fumigant activity in the two materials at the same temperature. The efficacy of PH3 was not related to the moisture content of wood. Sorption of PH3 was not affected by the moisture content in 3 different woods. The sorption rate or loss rate of PH3 increased with the volume ratio of pine wood. Phosphine adsorbed onto wood weakly, indicating that the gas, as a fumigant, might be useful for controlling termite infestations in quarantine situations.