Growers are being advised to check root disease levels prior to sowing so they can plan paddock suitability and variety choice.

Western Australia Department of Agriculture nematologist Vivien Vanstone said making an assessment now would help to maximise crop potential and yield return this season.

"Understanding disease levels is an important aid in planning for future seasons, as disease levels particularly for root lesion nematode, can rapidly increase under a susceptible crop variety," Dr Vanstone said.

"Testing soil offers a pre-season predictive indication of diseases present and their levels, so that risks can be determined and rotation and other management practices planned accordingly," she said.

The test, known as the PreDicta-B test, can measure levels and indicate potential risks from rhizoctonia, take-all, root lesion nematodes (RLN), and cereal cyst nematode (CCN).

However, Dr Vanstone warned that the PreDicta-B test was currently designed to detect only the two most common species of RLN (Pratylenchus neglectus and P. thornei) and several other species have been found in WA cereal cropping areas.

She said that the other species would not be picked up by the PreDicta-B soil test, which may explain an unexpected low or negative PreDicta-B test result for RLN. AGWEST Plant Laboratories can also test for RLN in soil.

Dr Vanstone said both the AGWEST and PreDicta-B tests are valid but results needed to be carefully assessed before deciding on management options such as crop rotations. She said it was also advisable to discuss the results with an agronomist who can put them into a regional or even farm-specific context.