Laboratory Exercise - Sampling

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

     2.   Reliability of population estimates.
       a. Work in pairs.
       b. Use the 30 cm x 2.5 cm diam soil tube to sample 2 rows of beans.  
          Remove 10 cores of soil from the root zone of the plants as a
          composite sample.
       c. Take a composite sample of 10 cores of soil to represent the whole 
          bean field.
       d. Clearly label your samples and store in an insulated box.
       e. Class will work together to extract nematodes from soil samples by 
          elutriation and sugar-centrifugation.  (Use a standardized quantity of
          soil).
       f. Each group will identify and count the predominant species of 
          plant-parasitic nematode in their samples (I hope there is a
          predominant species, otherwise we will select a microbivorous   
          species).
       g. Determine the spatial pattern of the selected species in the field 
          from abundance in 2-row samples.
       h. Determine the reliability of a single composite sample from the field
          on the basis of the range and variance of individual sample
          estimates.

     3.   Sampling nematodes associated with plant tissue. 
       a. Select from the tools provided to obtain a sample of the feeder roots
          of a tree, a shrub, and a grass. 
       b. Gently wash the roots from the soil and examine the root surface
          under the microscope for the presence of nematodes.
       c. Stain the roots in acid-fuchsin/lactic acid and examine them for 
          nematodes on the surface and inside the tissues.  What are the 
          problems associated with woody tissues?

     4.   Water and benthic sampling.
       a. Obtain a water sample from Putah Creek.  Sieve the nematodes from the
          water and concentrate into a jar in the field.  Remember that these 
          nematodes may be active swimmers - does that restrict the techniques
          you might use?
       b. Obtain a sample of the bottom deposits from Putah Creek using an     
          improvised dredge.  Place the sample in plastic containers. 
       c. Extract nematodes from the benthic sample by Decanting and Sieving.  
          You may need to devise an additional step if the sample is not clear
          enough for analysis.
       d. Identify the nematodes in the water and benthic samples at least to 
          Order using the approach suggested by Dr Maggenti.

     5. NEMAPLEX Exercise
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