Hot water immersion of Allium hookeri roots for the control of the plant parasitic nematodes Meloidogyne javanica and Pratylenchus coffeae

Nematodes are important quarantine pests of bulbous plants such as hooker chives. Although control methods such as fumigation, chemical immersion, and heat are often applied, it has proved difficult to disinfect nematodes from plant roots in quarantine. As heat treatment has been successfully useful for the control of nematodes in other agricultural products in quarantine, we investigated the susceptibility and mortality rates of Meloidogyne javanica and Pratylenchus coffeae, which infest hooker chive roots, using a hot water immersion method. Heat damage to the hooker chive roots was noticeable at temperatures over 50°C. Temperatures for the effective time to kill 99% at 1 min (ET99) for M. javanica and P. coffeae juveniles were 49.3°C and 49.1°C, respectively. However, the time to kill 99% of M. javanica eggs at 48°C and 49°C were 27.0 min and 8.3 min, respectively. Using a thermal equilibrium formula, the optimum commercial scale condition, in a 1400-L chamber, for nematode control without associated plant damage was water immersion at 48.2°C for 30 min or at 49.2°C for 13 min with a filling ratio less than 12%. This result can be applicable for the nematode disinfestation of hooker chive roots in plant quarantine.