NEMATOLOGY 100   -  FINAL EXAM      Name:
                                
                 December 9, 1992        2 hours

   1.  (10 points)
   Describe the several general mechanisms by which fungi parasitize
   nematodes.  Provide examples where possible.

   2.  (10 points)
   Explain Roberts' concept of the frequency for which host plant
   resistance is likely to be found for nematodes with different
   feeding habits.

   3.  (15 points)
   Describe the life cycle and host range of the citrus nematode.
   Provide a brief description of various approaches to management
   of this nematode.

   4.  (10 points)
   Suggest options for using natural plant compounds such as root
   exudates, plant constituents, or other plant-derived materials in
   nematode management.

   5.  (10 points)
   Name two nematode genera in different Orders in which hyperplasia
   is induced in root tissues.  What symptoms are associated with
   the hyperplasia in the host plants of these nematodes.

   6.  (10 points)
   Grapevine leaf-curl virus appears to be spreading slowly in a
   vineyard.  The vector is unknown.  Describe the evidence you
   would need to determine whether the virus is being transmitted by
   a nematode.  What types of nematodes would you suspect as
   potential vectors?

   7.  (10 points)
   Yields, and consequently net crop value, of lettuce are
   diminished by Longidorus africanus at the following preplant
   population levels:

            population level          crop value ($/acre)
                    0                       1000
                  100                        950
                  200                        900
                  300                        850
                  400                        800
                  500                        750
                  600                        700
                  700                        650
                  800                        600
                  900                        550
       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.

   8.  (10 points)
   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.

   9.  (15 points)
   Explain features of the life-history strategies of the
   Meloidogyninae and Heteroderinae that favor the success of
   nematodes in each subfamily in annual crop agriculture.