Mechanism of the nematicidal effect of essential oil from Cinnamomum cassia on Meloidogyne incognita juveniles

Essential oils (EOs) have been widely acknowledged as potential candidates for the formulation of environmental safe crop pesticides, also including nematicidal products. In this study, an EO from Cinnamomum cassia was investigated for its toxicity to infective juveniles (J2) of the root knot nematode Meloidogyne incognita by soaking or fumigation in vitro assays. Nematode J2 were exposed for 4, 8 or 24 h to 12.5-100 µg mL-1 concentrations of the EO. The highest concentration of C. cassia EO induced above 93% mortality already after 8h incubation. At the 50 µg mL-1 concentration, J2 mortality was above 60 and 94% after 8 and 24 h contact with the EO solutions. A 24-hour exposure by fumigation to 12.5-100 µg mL-1 EO concentrations was also effective, although mortality rates were lower than in contact experiments. A 24-hour immersion or exposure to vapors of the 25 µg mL-1 EO solution resulted in 20 and 37% mortality rates, respectively, and most of the alive nematodes appeared immobile. This subleth