A nematode count, combined with identification of the nematode species present, is the most accurate way to diagnose a nematode problem. Soil samples should be taken before the crop is planted. The area should be sampled on a grid, and the sub-samples mixed gently in a container. Each sub-sample should represent the upper 20cm of soil. From this mixture, remove about 500g of soil and seal it in a plastic bag for submission to:
AGWEST Plant Laboratories
3 Baron-Hay Court
South Perth WA 6151
Phone: +61 (0)8 9368 3721
An analysis will be performed, and the results interpreted by an expert adviser. There is a charge for this service. Plant roots can also be investigated for symptoms of nematode infestation, which is useful when planning future plantings in a nematode-infested area.
Exotic nematode species
There are currently two major nematode species of quarantine concern to Western Australia: the potato cyst nematode and the stem and bulb nematode.
Potato cyst nematode
There are several types of cyst-forming nematode, but potato cyst nematode (Globodera rostochiensis) poses a threat to the Western Australian potato industry. It has been identified in isolated areas of some Australian potato fields and has the potential to cause significant damage to the Australian potato industry through crop losses and the loss of export markets. Potato, eggplant and tomato crops are all affected by this nematode.
Potato nematode cysts can remain dormant in the soil for up to 30 years. A cyst is the dead body of the female, and may contain up to 500 eggs. Means of dispersal or introduction are through infested soil adhering to machinery, shoes or on plant roots. The nematode could also be introduced from infected seed potatoes or tubers. A diagnostic symptom of this nematode is the appearance of round, pinhead-sized cysts on potato roots around the time of flowering. The female nematodes are white when alive, but turn yellow to golden to brown as the cyst matures. Infection does not cause roots to form galls. In heavily infested soils plants have reduced root systems, develop nutrient deficiencies and consequently display poor growth and wilting. In fields of crops plant symptoms are usually patchy due to uneven distribution of the nematodes. Affected plants are more susceptible to infection by fungal pathogens and may age prematurely.
Stem and bulb nematode
This is more a pest of broad-acre crops, and currently occurs in Victoria and South Australia. This nematode would be a serious threat to agricultural production if introduced to Western Australia. Stem nematodes (Ditylenchus) attack the crown or stem base of susceptible crops like oat, faba bean, field pea, lentil, or canola. Symptoms include poor emergence, stunting, swollen stem bases, and yellow or brown streaks on leaves. These nematodes could be introduced through infected seed, bulbs, or soil.
It important not to introduce any seeds or plant material from interstate or overseas unless proper channels have been used and they meet with quarantine guidelines. Unless in advanced stages, nematodes are very hard to detect visually.
If exotic nematodes are suspected please phone the Department of Agriculture and Food’s Pest and Disease Information Service on Freecall: 1800 084 881.