NEMATOLOGY 100 Name:
FINAL EXAM
December 14, 2000, 2 hours
(100 points total; 50 % of overall grade)
1. (10 points)
Which feeding-habit groups of plant-feeding nematodes commonly exhibit resistance to desiccation? Use examples of genera, species, life stages, host crops and geographic locations where it may be important. Indicate the agricultural significance of this survival mechanism in each case.
2. (10 points)
Describe the life cycle of a plant-parasitic nematode that is vectored by an insect.
3. (10 points)
and Radopholus similis 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.
4. (8 points)
True (T) or False (F)
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Several types of plant viruses are vectored by the pin nematodes, Paratylenchus spp. |
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Sexual reproduction is more common in the cyst nematodes than in the root-knot nematodes. |
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Males of Rotylenchulus reniformis and Tylenchulus semipenetrans are capable of passing through several developmental stages without feeding. |
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Nematophagous fungi are present in many soils but may be below suppressive levels |
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Mesocriconema xenoplax feeds on roots of woody perennials and is associated with increased severity of bacterial canker in peach. |
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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. |
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Globodera rostochiensis and Anguina tritici are nematodes with extensive host ranges. |
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Two of the characters separating the Nematoda from other phyla of animals are that they are non-segmented and pseudocoelomate. |
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5. (10 points)
What are the various above-ground signs and symptoms associated with root-feeding nematodes? How would you determine that the symptoms result from nematode damage rather than some other cause?
6. (10 points)
Explain how increasing the organic matter content of soil might enhance suppression of nematode populations by biological antagonists.
7. (10 points)
Discuss the efficacy and constraints associated with flooding the soil for nematode management.
8. (12 points)
Indicate which of the following nematicides are:
(note: there may be more than one answer in each case)
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Compare life-history strategies in nematodes in the subfamilies Meloidogyninae and Heteroderinae.
10. (10 points)
What factors will you consider in developing crop rotation systems for management of plant-parasitic nematode population levels? Discuss the use of this approach for the dagger nematode, Xiphinema index, and the soybean cyst nematode, Heterodera glycines.
11.
Any (constructive!) suggestions for improvements in Nemaplex will be appreciated.
From Nematology 100, Fall 2000:
A take-home message to share with family and friends during the festive season:
In 1914, N.A. Cobb wrote:
".....if all the matter in the universe except the nematodes were swept away, our world would still be dimly recognizable, and if, as disembodied spirits, we could then investigate it, we would find its mountains, hills, vales, rivers, lakes, and oceans represented by a film of nematodes. The location of towns would be decipherable, since for every massing of human beings there would be a corresponding massing of certain nematodes. Trees would still stand in ghostly rows representing our streets and highways. The location of various plants and animals would still be decipherable, and, had we sufficient knowledge, in many cases even their species would be determined by an examination of their erstwhile nematode parasites."
In the new the millennium we can provide detail to Cobb’s pictorial prose by adding that, with present and emerging knowledge, fields in which the soils have been managed in a sustainable manner would be apparent, likewise those in which the soils are damaged by misuse of pesticides or irreversibly polluted with heavy metals. Areas in which the soils have increased in salinity, acidity and eutrophication would be evident as would those with undisturbed and pristine habitats which warrant the highest priority for protection. Our synthesis of the ecological function of nematodes in soil ecosystems has progressed to the extent that we can assess nematode faunal assemblages to measure the impact of stressors which threaten the functioning of soils, we can predict crop losses and can provide advice on cropping sequences and soil management practices so that sustainable optimal yields can be attained [....or can we?].