NEMATOLOGY 100 Name:
December 8, 2003, 2 hours
(100 points total; 50 % of overall grade)
1. (15 points)
Discuss the methods by which plant and soil nematodes survive resource limitation and adverse environmental conditions.
In your discussion, provide examples of genera, life stages, host crops and geographic locations where the survival mechanisms may be important and contribute to the agricultural significance of the organism.
2. (15 points)
What factors will you consider in developing crop rotation schedules for various plant-parasitic nematode species? Discuss the use of this approach for the sugarbeet cyst nematode, Heterodera schachtii, and the lesion nematode, Pratylenchus vulnus.
3. (10 points)
The foliar nematode, Aphelenchoides fragariae is found distorting leaves in a greenhouse that produces ornamental ferns for the restaurant industry. Provide advice to the producer regarding management or control of the problem.
4. (10 points)
The pin nematode has received more than usual attention and discussion in this class. Describe the life cycle of the pin nematode, its survival strategies, and the nature and severity of the damage that it causes to host plants.
5. (10 points)
True (T) or False (F)
a. Several types of plant viruses are vectored by spiral nematodes, Helicotylenchus spp.
b. Sexual reproduction is more common in the cyst nematodes than in the root-knot nematodes.
c. Males of Rotylenchulus reniformis, reniform nematode, and Tylenchulus semipenetrans, citrus nematode, are capable of passing through several developmental stages without feeding.
d. Nematophagous fungi are present in many soils but may be below suppressive levels
e. Soil fumigants such as 1,3-Dichloropropene (Telone) should be applied in wet soils because they move through water much faster than through air spaces.
f. Globodera rostochiensis and Anguina tritici are nematodes with extensive host ranges.
g. Two of the characters separating the Nematoda from other phyla of animals are that they are non-segmented and pseudocoelomate.
h. Nematodes of the genus Mononchus (Order Mononchida) attack higher plants by piercing root cells with their needle-tipped stylets.
i. Host-plant resistance has been identified and developed in cultivated plants most commonly for root-knot and cyst nematodes.
j. The stunt nematodes, genus Tylenchorhynchus, are important sedentary endoparasites of grapevines.
6. (15 points)
Describe the development of the feeding site in the genera Globodera and Meloidogyne.
What are the differences between the genera with regard to life history strategies?
7. (10 points)
Describe the proposed causality of bacterial canker of Prunus spp. (almonds and peaches), in California. What biological and environmental factors seem to play a role in the disease?
8. (15 points)
What are the various beneficial effects that cover crops might have in management of populations of plant-feeding nematodes? Also, Provide cover crop examples, where possible. Indicate any disadvantages in the use of cover crops.