Effects of Three Soil Fumigants on Meloidogyne incognita（Tylenchida: Meloidogynidae）Second-stage Juveniles and Eggs under Different Temperature Conditions

Changes in the fumigation efficacy with nematode stage and temperature were investigated using the three main fumigants currently used in Japan（chloropicrin, 1,3-D, and MITC）on Meloidogyne incognita（Kofoid et White）Chitwood（Tylenchida: Meloidogynidae）2nd-stage juveniles（J2）and eggs under various temperature conditions. An in vitro experiment under 5, 15, and 25°C temperature conditions showed the EC50 and EC90 of the three fumigants increased with a lower temperature. Regardless of the temperature condition, chloropicrin showed a very remarkable decrease in susceptibility in targeting eggs compared with J2. The differences in the susceptibility of 1,3-D between J2 and the egg became larger as the temperature decreased； the EC90 value of the eggs at 5°C was 10 times that of J2. The sensitivity of MITC to eggs was lower than that of J2 only at 5°C, but the difference was within 5 times the EC90 value. These trends in vitro were supported by field tests conducted in the summer and winter targeting the eggs remaining in the soil, which showed decreased efficacy in winter fumigation despite an increased accumulative concentration in the soil. The problem in the winter fumigation for the remaining eggs became clear.