|
|
Class
|
Secernentea
|
| Order |
Tylenchida |
| Superfamily |
Tylenchoidea |
| Family |
Hoplolaimidae |
| Genus |
Rotylenchulus |
Reniform
nematode is a very common, damaging pest
of many plants in subtropical/tropical soils and sometimes occurs in protected
temperate soil.
The first report that R. reniformis is pathogenic to
sweetpotato was made by Martin (1960). In sweetpotato, losses range from 44-60%,
depending on initial population.
The reniform nematode
causes root necrosis resulting in severe root pruning and subsequent dwarfing of
plants. Fibrous or feeder roots are mostly attacked which may reduce the
absorption ability and other physiological functions of the plant. This may lead
to stunting, yellowing and wilting. In some cases, the nematode may
produce lesions, distortions or cracks on storage roots which reduce
marketability.
R. reniformis is sexually
dimorphic. The immature female is free
in soil, measures 0.3-0.5 mm long, and C-shaped when killed by heat. The lip
region is rounded to conoid, continuous with the body contour and moderately
sclerotised. The stylet is 10-20 µm long, of moderate strength and with small
rounded basal knobs. There is opening of dorsal oesophageal gland, about a
stylet length, behind the stylet base. The oesophagus has well developed median
bulb and elongated (4-5 body widths) gland lobes, overlapping intestine
laterally and ventrally. The vulva posterior (V= 58-72) has paired, opposed
gonads, each with a double flexture in the ovary. The tail conoid with
rounded terminus is 2-3 anal body widths long. The mature female is
semi-endoparasitic in roots, greatly swollen, irregular to kidney-shaped, and
has enlarged gonads occupying much of body. The male lip sclerotisation and
stylet are much weaker than the immature female. Its oesophagus
degenerates and it has a tail similar to immature female, has small adanal
bursa, slender and with curved spicules.
Juveniles of the reniform nematode are differentiated within
the egg and undergo one moult before the second stage juveniles hatch. Three additional moults occur without feeding while the juveniles are free
in the soil. Adult stage and egg production occur 16 days after
inoculation in susceptible cultivars. The life cycle from egg to egg is from
22-29 days in susceptible cultivars such as V20-436.
Male and female nematodes can survive in
air-dried soil kept at 20-25oC for 7 months. Local dissemination is
through infested soil. Distribution is limited by low winter temperatures, and
nematode and disease development are both greater at 29.5oC than at
15, 21.5 or 36oC.
Very wide host range including weeds. Major
host are soybean, cowpea, cotton, pineapple, sweetpotato, cassava and other
vegetable crops.
Cultural control
Crop rotation.Non-host crops or
resistant crops can be planted when nematode population is high.
Use of organic
amendments.
Use
of trap and antagonistic crops. Planting Tagetes erecta and
Crotolaria spectabilis in nematode infested soil has been found effective
against the nematode.
Biological control
Paecilomyces lilacinus, a fungal egg
parasite was found effective against the reniform nematode.
Host-plant resistance
The
following Philippine cultivars/lines are found resistant to the reniform
nematode: CI 951-6, BNAS 551, VSP-1, V29-1166, CI 916-455, UPLB 80, Kabiti and
CI-950-27.
Chemical control
Several nematicides have
been reported to be effective against the reniform nematode. Examples are
Nemagon, Mocap, Dasanit, Nemacur, Furadan, Temik, Vydate.
Ayala, A. and Ramirez,
C.T. 1964. Host-range, distribution and bibliography of the reniform nematode Rotylenchulus
reniformiswith special reference to Puerto Rico. J. Agric. Univ. P.R.
48:140-161.
Birchfield
and Martin, 1968. Evaluation of nematicides for controlling nematodes of
sweetpotatoes. Plt. Dis. Rept. 52:127-131.
Dela
Cruz, C.S.1988. Reactions of sweetpotato (Ipomoea batatas Lam.) cultivars
to reniform nematode, Rotylenchulus reniformis,
and determinants of resistance mechanisms. M.S. Thesis. UPLB. 68 p.
Evans,
K, D. L. Trudgill and J. M. Webster. 1993. Plant Parasitic Nematodes in
Temperate Agriculture. University Press, Cambridge. 648 p.
Galano,
C. D., R. M. Gapasin and J. L. Lim. 1996. Efficacy of Paecilomyces lilacinus isolates
for the control of root-knot nematode (Meloidogyne incognita (Kofoid and
White) Chitwood) in sweetpotato. Annals of Tropical Research 18: 4-12.
Gapasin,
R. M. and R. B. Valdez. 1979. Pathogenicity of Meloidogyne spp. and Rotylenchulus
reniformis on sweetpotato. Annals of Tropical Research 1:20-26.
Gapasin,
R. M. 1984. Resistance of fifty-two sweetpotato (Ipomoea batatas (L.)
Lam.) cultivars to Meloidogyne incognita and M. javanica.
Annals of Tropical Research 6: 1-19.
Martin. 1960. The
reniform nematode may be a serious pest of the sweetpotato. Plt. Dis. Rept.
44:216.
Sasser,
J. N. and C. C. Carter. 1985. An Advanced Treatise on Meloidogyne. Vol.
I: Biology and Control. North Carolina State University Graphics. 422 p.
Sasser,
J. N. 1989. Plant Parasitic Nematodes: The Farmer’s Hidden Enemy. University
Graphics, North Carolina State University, Raleigh, N. C. 115 p.
Contributed
by: Ruben Gapasin |
