December 12, 1990        2 hours

      (10 points)
  1.  Describe the reproductive strategies of plant-parasitic nematodes,       
      giving examples of genera or species.  What are the advantages and 
      disadvantages of each strategy to the nematode species in relation to 
      conventional practices in intensive agriculture?

      (10 points)
  2.  Describe the plant damage and economic importance of a plant-parasitic 
      nematode that is vectored by an insect.  Name the vector.

      (10 points)
  3.  Describe the stimuli, their sources, and the responses that result in 
      syncytia associated with infection by Heterodera or Globodera.

      (5 points)
  4.  What are the various above-ground symptoms associated with nematode 
      parasitism of plants?

      (15 points)
  5.  A cotton variety that is normally resistant to Fusarium  loses its 
      resistance when planted in a particular field in Kern County.  The 
      variety performs well in this field when the soil is treated with the 
      soil fungicide Chloropicrin. Describe the experiments that you would 
      undertake to determine whether nematodes are the cause of the loss of 

      (10 points)
  6.  Flooding of fields is sometimes suggested as a method of control for 
      plant-parasitic nematodes.  How would nematodes be killed?  What
      are the constraints and possible impacts of this approach?

      (10 points)
  7.  Describe the principle and discuss the mechanisms of nematode management 
      through the use of trap crops.

      (15 points)
  8.  The following nematodes are detected in a field to be planted to almonds 
      in a sandy soil in Merced County, California: Heterodera schachtii,
      Meloidogyne incognita, a predaceous nematode, and at least three species
      of microbial-feeding nematodes.  Recommend any nematode control 
      procedures that you think appropriate, environmentally sound, and 
      economically justifiable.  Indicate the nematodes that you are targeting
      with each procedure.

      (5 points)
  9.  List some predators of nematodes and indicate their phyla.

      (10 points)
 10.  Ditylenchus dipsaci, Ditylenchus destructor, and Ditylenchus angustus
      are parasites of plants.  Name at least one host plant of each and 
      indicate the part of the plant where you would expect to find each of
      the nematode species.