Pratylenchus nematodes, or root lesion nematodes (RLN), are tiny worms with hefty appetites and they are eating into cereal yields by up to 15 per cent across almost half the WA wheatbelt.

Just one nematode per gram of soil can stall crop growth and cause uneven patches in paddocks.

Promisingly, eastern states research discovered rotations using resistant legumes, such as faba beans and field peas, could control nematode numbers. WA trials showed nematode levels in wheat grown after field peas or faba beans were much lower than in wheat following wheat.

However, WA is home to a diverse array of RLN species, which challenges rotational strategies because different species are likely to prefer different host plants. All species can be found in association with intensive cereal cropping, with wheat the most susceptible to the identified major, damaging RLN species.

WA graingrowers, therefore, face a tense chess game with nature and must send forth the right pawns and soldiers to protect their cash kings of wheat and barley.

Department of Agriculture research, supervised by Dr Vivien Vanstone and supported by growers and the Federal Government through the Grains Research & Development Corporation (GRDC), is striving to identify the winning strategy.

Existing wheat varieties vary in their susceptibility to the major RLN species, P. neglectus and P. thornei, with Westonia, Carnamah, Camm and Brookton among the most at risk, while Wyalkatchem, Perenjori, Cascades and Nyabing display some resistance.

Other crops with resistance to the two main RLN species, including field peas, faba beans, lupins and triticale, can also be used in rotations to reduce nematode levels.

Sean Kelly examined the resistance profile of 25 field pea varieties for their rotational defence capabilities in thinning nematode populations. Dundale and Parafield were the most resistant to P. neglectus. Research will determine optimum varieties of major crops for nematode control.

Rotating resistant or moderately resistant crop varieties best reduces soil nematode levels and consequent crop losses. Susceptible crops should be avoided where nematode levels are high, while resistant crops can help prevent nematode build-up.