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.