Endoparasitic nematodes in cropping soils of Western Australia

Soil samples were collected in Western Australia from cereal fields at about harvest time to determine levels of the endoparasitic nematodes, Pratylenchus and Heterodera. A systematic survey in 1997 and 1998 centred on the 40 shires with the highest proportion of cereal cropping. One hundred and eighty samples were collected in 1997 and 227 in 1998 at 10-km intervals along north-south transects 35 km apart. A targeted survey in 1997 included 98 soil samples from fields selected by growers as having poor productivity without an evident cause. No Heterodera cysts were found in any survey sample but these could be extracted from soils previously known to be infested. Pratylenchus neglectus was most commonly detected followed by P. thornei and P. zeae. Populations identified as P. brachyurus, P. penetrans, P. scribneri, and an undescribed species similar to P. thornei were also found. Overall Pratylenchus was extracted from 63% of samples (mean 1.1, median 0.3, max. 22.0/mL of soil). Maps of the data indicate that Pratylenchus populations were aggregated with some areas having relatively light infestations. There was a positive relationship with the intensity of cereal cropping and a negative relationship with pulse cropping. The findings indicate that potentially damaging Pratylenchus numbers occur in a significant proportion of fields and highlight the need to develop and implement strategies to lower population densities.