December 16, 1989        2 hours

    (4 points)
    1.  Sexual dimorphism is found in which of the following genera?





    (10 points)
    2.  Describe the life cycle of a plant-parasitic nematode that is vectored 
        by an insect.

    (8 points)
    3.  True (T) or False (F)

          a.  A species of Anguina is sometimes associated with a bacterial
              infection of grasses caused by Corynebacterium.

          b.  Nematode-virus relationships are non-specific and a
              nematode such as Longidorus elongatus will vector all strains of 
              Tobacco Rattle virus.

          c.  Males of Rotylenchulus reniformis and Tylenchulus semipenetrans
              are capable of passing through several developmental stages 
              without feeding.

          d.  Species of Hoplolaimus behave as migratory endoparasites on
              some hosts.

          e.  Mesocriconema xenoplax feeds on roots of woody perennials and
              is associated with increased severity of bacterial canker in 

          f.  Soil fumigants such as 1,3-Dichloropropene (Telone) move
              through the air spaces in soil much faster than through water.

          g.  Globodera rostochiensis and Anguina tritici are nematodes with a
              narrow host range.

          h.  Two of the characters separating the Nemata from other phyla of
              animals are that they are non-segmented and pseudocoelomate.

    (8 points)
    4.  Describe the stimuli and responses that result in giant cells
        associated with Meloidogyne infection.

     (12 points)
     5.  Briefly discuss the economic importance, distribution, host range, 
         injury to host, relation to host tissue, biology as influenced by 
         physical environment, and control of the following:

      a. Bursaphelenchus xylophilus 

      b. Hemicycliophora arenaria 

      c. Xiphinema index

      (8 points)
      6.  What factors will you consider in developing crop rotation for various
          nematode groups?  Discuss the use of this approach for the genus 
          Pratylenchus and the genus Globodera.

      (12 points)
      7.  Based on your knowledge of nematode control, biology, distribution and
          host ranges, what control measures are available and practical for
          the following nematode diseases:

      a.  Globodera rostochiensis on potatoes

      b.  Meloidogyne incognita on tomato

      c.  Ditylenchus destructor on potato

      d.  Aphelenchoides ritzemabosi on chrysanthemum

      e.  Pratylenchus vulnus on roses

      f.  Tylenchulus semipenetrans on citrus

      (4 points)
      8.  Indicate which of the following nematicides are:
      a.  halogenated hydrocarbons
      b.  fumigants
      c.  nonfumigants
      d.  organophosphates
      e.  carbamates
          (note there may be more than one answer in each case)

(i)  Telone

(ii)  Temik 10G

(iii)  Vapam

(iv)  Furadan

      (8 points)
      9.  Outline the approaches that you anticipate will be necessary and 
          available for the management of plant-parasitic nematodes on perennial
          crops in the 1990s.

       (8 points)
      10.  Briefly describe the modes of parasitism of the fungi that are 
           antagonistic to nematodes. Provide examples where possible.

       (8 points)
      11.  Preliminary experiments indicate that yield, and consequently crop
           value, of sweet corn is diminished by Longidorus africanus as
                  population level          crop value ($/acre)
                        0                       1000
                       10                        950
                       20                        900
                       30                        850
                       40                        800
                       50                        750
                       60                        700
           Estimate the lowest population density at which the use of a
           nematicide treatment costing $125/acre is profitable?  Assume that 
           the nematicide reduces the population level to zero so that maximum 
           crop value is attained after treatment.

       (10 points)
      12.  Describe the life cycle and feeding habits of nematodes in 
           the genus Radopholus.  Briefly describe the damage caused by a
           species of this genus to citrus.