Nematodes - not always the enemy, but can be an indicator of soil health

Mention of the word "nematode" generally brings notion of one of the most destructive turf pests that we have.

Nuturf nematodes
Mention of the word "nematode" generally brings notion of one of the most destructive turf pests that we have.
Research coordinated by the South Australian Research and Development Institute (SARDI) has shown that these free living nematodes are an indicator of soil health. Jyri Kaapro Bayer's Turf Consulting Manager, Jyri Kaapro, is a renowned personality in the Australian turf industry, having worked for the past 13 years in Research & Development at Bayer.

Plant parasitic nematodes cause a lot of turf damage and are very difficult to control. In recent years the entomopathogenic nematodes have brought the new concept of using nematodes to control a range of damaging turf insect pests like scarab beetles. Now it seems that nematodes can represent something else to turfgrass managers.

Soils not only contain plant parasitic nematodes but also a whole range of other free living nematodes. These nematodes represent four broad groups; bacterial and fungal feeding, predatory and omnivores. Research coordinated by the South Australian Research and Development Institute (SARDI) has shown that these free living nematodes are an indicator of soil health. 

The type and abundance of these nematodes in the soil is a reflection of the food sources which are available to them and this in turn is a reflection on the health of the soil.

Bacterial feeding nematodes are relatively small and complete their life cycle in a few days. Their populations build up rapidly in response to a food source and decline as rapidly when the food source depletes. Food sources increases following soil disturbance or the input of organic matter. Fungal feeding nematodes are also relatively small but have longer life cycles. They live on fungi that decompose organic matter as well as plant disease causing fungi.

The predatory and omnivore nematodes are much larger and can take several months to complete their life cycle. Well-structured and mature soils have larger populations of these nematodes. Their numbers decrease when soil disturbance occurs and it can take years for the numbers to return to their original levels.

"Healthy" soils will have all four groups of free living nematodes present. The determination of free living nematodes in soils to date has been a difficult and time consuming process. Nematodes are small and occur in very large numbers in the soil, their extraction and identification from soil samples involves microscopic work by experts. Work by SARDI is leading to a new method for analysing these nematode populations. SARDI has developed techniques to identify free living nematode populations in soil by DNA analysis.

For some years SARDI has offering a service for broad acre grain growers called Predicta B. This service analyses soil samples using DNA identification for a range of plant parasitic nematodes and plant diseases. The service is designed to be used before crop planting to determine the potential for issues with these pests and diseases. Then preventative management strategies can be implemented if the risk of a particular problem is considered to be high enough to warrant such treatment.  The analysis is rapid and cost effective and unfortunately for turfgrass managers very specific to cereal grain crops.

It is hoped that with the new tests being developed for free living nematodes along with the current Predicta B tests will lead to a tool which gives a rating of soil health. In time this technology may be come adapted for other plant production systems like turfgrass.