NEMATOLOGY 100 - FINAL EXAM December 16, 1989 2 hours (4 points) 1. Sexual dimorphism is found in which of the following genera? Pratylenchus Tylenchulus Tylenchorhynchus Globodera (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. Criconemoides xenoplax feeds on roots of woody perennials and is associated with increased severity of bacterial canker in peach. 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 follows: 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.