Nematology 100 Field Trip                      

 Rev 01/01/20

Purpose:  Field symptoms, field extraction and observation, discussion of practical detection, assessment and management issues:

Work in pairs.

Each group takes two samples from stratified area or group of plants.  Cores from a stratum are bulked, mixed and a subsample taken for extraction of nematodes.

We will be visiting several sites.  Please clean equipment between sites.

Extraction: 

• decanting and sieving for large nematodes

• direct observation for nematodes that exhibit signs or symptoms

• Seinhorst 2-flask method and sugar-centrifugation for less mobile nematodes.

Where a coarse screen is used in the extraction, is there any correlation with the amount of root detected in the sample and the presence of nematodes?

Purpose:  To demonstrate the tools available for sampling to detect and quantify nematode populations.  To test the reliability and precision of sampling procedures.

1.   Demonstration of sampling tools and their use (at the alfalfa site).

• Oakfield 2.5 cm diam soil tube - varying lengths and designs,  including automatic bagging and foot attachments.
• Veihmeyer sampling tube.
• Auger
• Gasoline powered auger.
• Shovel.

2.   Effect of extraction method on determination of species presence/abundance.   

• Work in pairs.
• In the grape rootstock trial, from one replicate plot of St. George rootstock, sample under a dripper.  Use a shovel to sample soil around feeder roots. 
• Are there symptoms of nematode feeding (root-tip galls)?
• One group extract nematodes from the soil by decanting and sieving with a 100 mesh sieve, followed by direct observation.
• One group extract nematodes from the soil by the Seinhorst 2-flask method followed by sugar-centrifugation (we will do this later on campus).
• Are there differences in the types and abundance of nematodes detected?

3.   Reliability of population estimates.

• Work in pairs.
• Use the 30 cm x 2.5 cm diam. Oakfield tube to sample a uniform stand of alfalfa. 
• Each student sample the field by taking 10 cores of soil to a depth of 15 cm from the root zones of plants as a composite sample to represent the alfalfa field.
• Clearly label your samples and store in an insulated box.
• Class will work together during a scheduled laboratory session to extract nematodes from 250cc soil subsamples by decanting, sieving and Baermann funnel techniques
• At the next laboratory period, each group will identify and count the predominant species of plant-parasitic nematode in their samples
• Determine the reliability of a single composite sample from the field on the basis of the range and variance of individual sample estimates.

     4.   Sampling nematodes associated with plant tissue.

• Sample walnut trees at the drip line.
• Use a shovel to collect soil and roots.
• Wash samples through a screen into a 2-liter Ehrlenmeyer flask.  Collect the roots caught on the screen for mist extraction in the laboratory to determine presence and abundance of migratory endoparasitic nematodes.
• Use Seinhorst 2-flask method followed by sugar-centrifugation to determine presence and abundance of migratory endoparasitic nematodes in the soil.

    5. NEMAPLEX Exercise

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