PLANT-PARASITIC AND FREE-LIVING NEMATODES ASSOCIATED WITH SUGARCANE IN NORTH QUEENSLAND

SURVEYS OF NORTH Queensland sugarcane soils indicated that root-lesion nematode (Pratylenchus zeae) was the most important nematode pest because it occurred in most fields and was often present at high population densities. However, the presence of root-knot nematode (Meloidogyne spp.) in sandy soils and the relatively widespread distribution of moderately pathogenic nematodes such as stunt nematode (Tylenchorhynchus annulatus), stubby root nematode (Paratrichodorus minor), ring nematode (various Criconematidae) and dagger nematode (Xiphinema elongatum) suggested that in most fields, several nematode species were feeding on roots and contributing to root health problems. With regard to the free-living nematode community, survey results showed that bacterial-feeding nematodes were much more common than fungal-feeding nematodes and numbers of omnivorous and predatory nematodes were relatively low. Collectively, these findings suggest that the biological status of many north Queensland sugarcane soils is relatively poor. In addition to having high numbers of plant-parasitic nematodes they have low numbers of fungal-feeding nematodes. This indicates that fungi are not an important component of the detritus food web and this has implications for the ecosystem services they provide: decomposition of recalcitrant forms of organic matter; aggregation of soil particles; enhancement of plant nutrient uptake; improvement of disease resistance in plants; and suppression of pests and pathogens. The lack of omnivorous and predatory nematodes also has implications for pest suppression, as these nematodes help regulate populations of plant-parasitic nematodes.