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. Mesocriconema 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.