Abstract

H. Y. Wu and L. B. Shi

Due to continuous cropping over many years, the root-knot nematode (Meloidogyne spp.) has become a severe pest in plastic film greenhouses in China. This study investigated the populations of root-knot nematode second-stage juveniles (J2) in comparison to other free-living soil nematodes in soils continuous cropped for different durations. Overall, the J2 population increased with the duration of continuous cropping. The number of J2 at different soil depths in soils cropped for 0 and 5 years was significantly lower than in soils cropped for 8 and 12 years (P < 0.05). In soils that had been continuously cropped for 8 and 12 years, the average number of J2 was 154.9 and 861.8 nematodes per 100 g dry soil, respectively. The J2 numbers increased with soil depth, being predominantly distributed at 20 - 30 cm soil depths. Free-living nematode populations also increased with soil depth. The percentage of J2 nematodes based on total nematode numbers was significantly higher in soils continuously cropped for 8 and 12 years than for plots cropped for 0 or 5 years (P < 0.05).