Interspecific and intraspecific competition in the potato cyst nematodes Globodera pallida and G. rostochiensis

The effects of interspecific competition between the potato cyst nematodes (PCN), Globodera pallida and G. rostochiensis, under variable population conditions were examined. PCN-susceptible potato cultivars were inoculated with single- and mixed-species populations of PCN. There was a significant difference in species multiplication between single- and mixed-species populations. Globodera rostochiensis multiplication in mixed-species populations was significantly lower than single-species populations. Density-dependent trials showed a significantly greater increase in multiplication of G. pallida at low inoculation densities relative to G. rostochiensis. These results indicate that G. pallida has a negative effect on G. rostochiensis populations and is the more successful species when competing. A staggered inoculation trial showed that the greater competitiveness of G. pallida was not wholly attributed to its later hatch. Globodera pallida outcompeted G. rostochiensis regardless of the timing of inoculation; however, G. pallida multiplication was lowest when plants were simultaneously inoculated with both species.