Nematode Close-up- Photo Credit: Dr J. Eisenback, Mactode Publications (mactode.com)
Nematodes, also known as eelworms, are mostly microscopic in size and have translucent, slender wormlike bodies that taper toward the head and tail. They are hard to see with the naked eye, but can be extracted from the soil using specialised techniques.
Plant-parasitic nematodes feed on plant roots and can decrease vine productivity. Therefore, it is important that nematode opulation pressure is assessed pre-planting, and when management inadvertently promotes the lifecycle of nematodes.
For example, legume cover crops are ideal hosts for nematodes, while others can provide a biofumigant effect and deter nematodes.
The analysis of soil samples for nematodes has to be carried out in a specialist laboratory. The information below suggests general guidelines for collecting nematode samples.
Sample sizes or sampling methods for different laboratories may vary. Check with the laboratory used to see if they request a certain quantity of soil, or specify a certain collection method.
Equipment
Shovel, bucket, plastic bags, recording sheet and pen, labels or permanent felt tip marker pen.
Timing
Spring to Winter, when an active host is present.
Method
1. Sample when soil is humid but not too damp, preferably after rain or irrigation.
2. A composite soil sample of 15 20 cores should be collected from about 0.5 hectare.
3. Discard the surface soil to minimise the infl uence of dried topsoil, weeds and cover crop.
4. Handling soil carefully, collect three soil and root samples from the middle vines in a panel at each sampling site:
• When sampling specifically for root-knot nematode, collect soil samples about 10cm from the vine, to a depth of depth of 30cm;
• When sampling specifically for dagger and root lesion nematodes, collect soil samples about 10cm from the vine to a depth of 60cm (especially in the deeper sandy soils) in mid to late Spring (October and November), when vine roots are actively growing.
The increased depth of sampling compensates for the greater variation in vertical distribution of root lesion and dagger nematodes, and includes layers most populated by dagger nematodes. The best time to sample grapevine roots for root lesion nematodes is December.
Approximately 1kg of soil is necessary from each site (the laboratory may request a smaller sub-sample from this bulk sample). Each sample must contain soil and/or feeder roots.
5. At each sampling point, alternate the side of the vine from which samples are collected.
6. Place each sample in a separate labeled bag and seal.
7. Store bags in a refrigerator at about 4°C until they can be sent for testing. Samples need to be assessed within two weeks, however as soon as possible after collection is preferable.
8. Check with your State Government Department of Agriculture or Primary Industries for contact details of suitable laboratories in your state or region (some contacts are provided below).
9. Check with the specifi c laboratory to make sure sample(s) can legally be sent.
WARNING: If you are within a Phylloxera Risk Zone (PRZ) or Phylloxera Infested Zone (PIZ) then consult the National Phylloxera Management Protocol.
