Collecting Soil and Plant Samples for Nematode Analysis
Note Number: AG1444
Published: July 2011
Plant-parasitic nematodes are found in soil, roots, stems, bulbs, leaves, buds and seeds. They have a very wide host range including field crops, fruits, ornamentals, grasses and weeds. These nematodes are microscopic, wormlike in appearance, and generally measure from 0.2 mm to 2.0 mm in length. The most commonly detected plant-parasitic nematodes are root-knot (Meloidogyne spp) (Figures 1 and 2), root-lesion (Pratylenchus spp) (Figure 3), leaf and bud (Aphelenchoides spp) (Figure 4), stem and bulb (Ditylenchus dipsaci) (Figure 5), spiral (Helicotylenchus spp) (Figure 6), stubby-root (Paratrichodorus spp) and dagger (Xiphinema spp) nematodes.
The above ground symptoms of nematode infected plants are patchy and stunted growth, yellowing, early decline and wilting. These symptoms may often be confused with nutritional and water deficiencies, or infection by fungi or viruses. An accurate diagnosis of nematode damage is necessary before any valid control recommendations can be implemented. It is important to follow the correct procedures for collecting and handling samples to ensure an accurate determination of nematode damage.
When to collect samples
The best time for sampling varies between crops, and is related to the growth stage of the crop and the objective of sampling. Many species of nematodes increase to high levels during the growing season and reduce to low numbers during the dry season. This is more easily seen in annual crops than in perennial and tree crops.
- Clean bucket for collecting samples
- Soil probe (Figure 7) or shovel/spade
- Plastic bags to hold 500 g of soil
- Waterproof marker
How to sample
Fallow or bare fields
Do not collect samples when field is dry or extremely wet. For sampling, the field should be divided into 1-2 hectare blocks.
Take about 20-30 cores/sub-samples of soil, at 15-20 cm depth from an area of 1-2 hectares. Collect these sub-samples at every 10-20 metres in a 'W' (Figure 8) or in a 'Zigzag' pattern (Figure 9). Place sub-samples in a bucket and mix thoroughly with hands, and collect a 500 g composite sample in a labelled plastic bag.
Nematodes do not necessarily occur uniformly throughout a field, therefore several sub-samples must be taken from across the field, and then combined. Collect 20-30 random sub-samples from each block of 1-2 hectares. Samples should be taken directly from the root zone. Mix sub-samples thoroughly and place 500 g of soil, with roots, in a plastic bag, for laboratory analysis. Because nematode damage within a crop can be patchy, collect samples from healthy plants, as well as from plants showing symptoms of decline. Keep these samples separate and label them as 'good' and 'bad' samples.
Trees and Shrubs
Collect lumps of soil from around the root zone containing feeder rootlets or intact root systems, and place them in a plastic bag. Samples should be collected from the upper 20-30 cm depth around drip rings (Figure 10). Take several sub-samples from each tree or shrub. A minimum of 500 g of soil, and 10 g or a handful of feeder roots, per sample is recommended. Thick woody roots, unless bearing galls or knots, are of little use for nematode analysis. Take samples separately from 'healthy' trees and from those showing symptoms of decline.
Pastures, Turfs and Lawns
Take several samples, from the top 10-15 cm of soil, from the edge of a declining patch. Follow the same sampling techniques described under field crops. Take separate samples from nematode 'affected' and 'healthy' areas to get a better picture of nematode distribution in the field.
Nurseries and Greenhouses
Nursery and greenhouse crops generally have little tolerance to damaging plant-parasitic nematodes. Replanting in nematode-infested containers or bare-root plant material usually results in spread of nematodes. Collect a minimum of 500 g of soil, including feeder roots if present. Leaf, stem, seed or other aerial plant material should be collected where symptoms are noticed and nematodes suspected. It is important to select from a number of affected plants, as these samples can be compared with healthy plants.
When nematodes are suspected in home gardens, collect representative samples with fine roots. If ornamental plants, submit whole plants where possible, otherwise leaves, bulbs or tubers etc.
Care of Samples
Place all samples in plastic bags to prevent drying. Generally, plant-parasitic nematodes remain alive at temperature between 5° C and 40° C, and die within seconds when exposed to temperatures above 50° C. Keep samples in a cool place at all times. Do not refrigerate samples. Do not leave samples exposed in the field, or in a vehicle, on very hot days. Do not wrap roots or any other plant material in damp tissue. Leave roots with soil in bag. Place other plant material in a separate plastic bag.
Label and Information
Label samples with identification numbers and provide the following information on a separate sheet of paper:
- Name and address of the grower as well as sender
- Crop plant, symptoms and estimated damage
- A sketch map of the diseased area and the sampling site, and also an indication of the topography of the field
- Cropping history of the field
- Fertilisers, pesticides and herbicides applied
- Relevant weather conditions and watering or drainage conditions.
It is necessary to provide the above information so the results of the analysis can be interpreted correctly and satisfactorily.
Where to send the samples
For nematode analysis, send the samples to the Crop Health Services laboratory address given below:
Crop Health Services,
621 Burwood Highway,
Or Postal Address:
Crop Health Services,
Private Bag 15,
Ferntree Gully Delivery Centre
Coyne, D.L., Nicol, J. M. and Claudius-Cole, B. (2007) Practical Plant Nematololgy: A Field and Laboratory guide. Shurtleff, M. C and Averre, C. W (2000) Diagnosing Plant Diseases Caused by Nematodes.
Contact/Services available from DPI
For further information, phone Crop Health Services on (03) 9210 9222 or fax (03) 9800 3521.
This Agriculture Note was developed by Lila Nambiar and John Wainer, Crop Health Services, Knoxfield in July 2011.