This document summarizes a study on using cover crops to manage the root-knot nematode (Meloidogyne incognita) in yam production systems. Pot and field experiments tested the effect of 10 cover crops on M. incognita populations and yam tuber damage. Results showed that tagetes, crotalaria, and aeschynomene cover crops significantly reduced nematode densities and yam damage, while lablab, mucuna, and cowpea supported high nematode populations. The document concludes that tagetes, crotalaria, and aeschynomene should be incorporated into yam farming to control root-knot nematodes.

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Management of Meloidogyne incognita in yam-
based cropping systems with cover crops
by
A.O. Claudius-Cole,B. Fawole,R. Asiedu and
D.L. Coyne
Crop Protection and Environmental Biology, University of Ibadan,
International Institute of Tropical Agriculture, Ibadan, Nigeria.
Presented by
Temitayo Oluwatosin, Aremu
May, 2015

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• Nigeria produces 70-76% of world yam
production (FAO data, 2007,1985).
• Yams contributes ~30% of the
calorie intake in W. Africa (FAO, 2007)
Uses
• Feed for livestock
• Food for humans
• Pharmaceutical benefits
• Socio- Cultural value
Introduction
Pounded yam and egusi
Boiled yam and egg
Contraceptives

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Yam Production Constraints
• Availability and cost of seed yam
• Cost of labour
• Pests and diseases
– Mealybugs
– Yam beetles
– Anthracnose
– Nematodes
• Scutellonema bradys
• Meloidogyne spp.
• Pratylenchus coffeae
Pratylenchus coffeae
Meloidogyne spp.
Scutellonema bradys

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Impact of Nematodes on Yam
• 47% of tubers on sale in Nigeria markets are infested with
S. bradys (Wood et al.,1990)
• 34%-52% reduction in price of Meloidogyne
infected tubers (Nwauzor and Fawole, 1982)
• Yam dry rot causes reduction in quantity,
market value, storage & edible part of tubers
Infested tuber Healthy tuber
Galled tuber
Dry-rot on cut yam tuber

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Objective
• To evaluate the use of some cover crops as inter-crops, for
root-knot nematode management in yams.

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Materials and Methods
• Four cultivars of Dioscorea spp;
• D. Alata: TDa 294 (Hawaiian) and TDa 92-2 (Shagbe)
and
• D. Rotundata: TDr 608 (Nwopoko) and TDr 93-
3(Danacha)
• 10 cover crops: Aeschynomene histrix ,Cajanus
cajan , Centrosema pubescens , Crotalaria juncea
,Lablab purpureus ,Mucuna pruriens , Tagetes
erecta , Pueraria phaseoloides ,Stylosanthes
guianensis and Vigna unguiculata(Ife Brown)

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Materials and Methods cont…
• Examples of some of the plants used as cover crops.
Crotalaria juncea
Tagetes erecta
Aeschynomene histrix
Centrosema pubescens
Stylosanthes guianensis

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Pot Experiments
• Tubers were cut into 50 g setts and pre-treated
• Planting was in 23 cm diameter pots containing 5 l of
steam-sterilized soil.
• Cover crops planted 1 week after transplanting yams
• Inoculation was with 5000 eggs using a syringe applied
directly into four holes made in the soil and zero
nematodes as control.
• RCBD with 6 replicates in the screen house

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Field experiments
• Yam setts were cut into 150 g setts, treated,
pre-sprouted before transplanting
• Cover crops were planted one week after
transplanting
• Field experiment was RCBD in split plot layout
• 4 replicates with 10 plants per plot

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Materials and Methods cont…
• Extraction of eggs/juveniles of RKN from galled roots
of Celosia argentea (Hussey & Barker 1973)
• Inoculation of 10,000 eggs of M. incognita per plant
and no-nematode control on the field
Galled Celosia roots
Extract poured through sieves
NaOCl

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Data Collection
• Tubers were harvested 6 MAP, weighed and scored for
nematode damage using 1- 5 damage scale
• Extraction of Meloidogyne spp. from
tubers and roots (Hussey and Baker 1973)
• Extraction from soil via modified
Baermann tray method (Coyne et al., 2007).
• Nematodes were counted with a dissecting microscope
• Data recorded and Reproductive factor(RF) determined;
where Pf/Pi (Pf = final population and Pi is initial nematode
population)
Soil Extraction

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Data Analysis
• Transformation of percentage data and nematode
counts using arcsine or Log (x þ 1) where appropriate.
• All data were subjected to analysis of variance
(ANOVA)
• Statistical analysis was conducted using SAS program
(SAS Institute Inc., 2001)
• Means was separated using Student Newman Keuls
(SNK) at 5% level of significance and standard error
were used where appropriate.

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RESULTS

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Table 1. Effect of Cover Crops on Tuber Damage, Number of
Meloidogyne incognita in Tuber, Soil, and Roots of Cover
Crops and Nematode Reproductive Factor in Pot Experiment
Cover crop Tuber
damage
score
2MAS
M. incognita
Population in
tuber (5 g)
2MAS
M. incognita
Population in
Soil (100
cm3)
M. incognita
Population in
Root (5 g)
Reproducti
ve
factor (RF)
T. erecta 1.0d 12.6d 0.4d 0.4d 0.4c
C. juncea 1.0d 4.1d 0.7d 0.6d 1.0c
A. histrix 1.0d 11.1d 0.5d 0.8d 0.9c
S. guianensis 1.1cd 15.0d 0.9cd 10.1d 1.9bc
P. phaseoloides 1.2cd 80.4c 3.5b 9.2d 2.2bc
C. pruriens 1.3c 9.0d 0.6d 3.3d 1.8bc
C. cajan 1.4c 151.3bc 5.0a 27.2c 4.3b
No cover crop 2.4b 406.2a 1.2c 3.9b
L. purpureus 3.1a 229.8b 3.4b 151.6a 16.4a
V. unguiculata 3.3a 840.2a 5.5a 78.0b 12.5a

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Table 2. Effect of Cover Crops on Tuber Damage, Number of
Meloidogyne incognita in Tuber, Soil, and Roots of Cover Crops
and Nematode Reproductive Factor in Field Plots.
Cover crops
Damage
score of
yam tuber
(3 MAH)
Mean
number of
nematodes in
tuber (5 g)
Mean
number of
nematodes
in
soil(100cm3)
Mean number of
nematodes in
cover crops
roots(5 g)
Reproducti
ve Factor
(RF)
A. histrix 1.0d 13.4c 0.4d 0.3c 0.7c
T. erecta 1.0d 2.4c 0.0d 0.1c 0.2c
C. juncea 1.0d 0.0c 0.0d 0.1c 0.0c
M. pruriens 1.0d 25.7c 0.6d 0.9c 1.1c
C. pubescens 1.1d 33.3c 1.0d 3.0c 0.9c
P. phaseoloides 1.1d 46.7c 0.4d 1.5c 2.3c
S. guianensis 1.2cd 148.6bc 1.0d 0.9c 1.5c
C. cajan 1.5c 541.1b 8.2c 59.8b 32.5b
No cover crop 1.9b 392.1b 6.0c ---- 28.6b
L. purpureus 2.8a 1574.2a 10.5b 76.5b 67.8a
V. unguiculata 2.9a 1095.5a 16.3a 111.6a 53.8a

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Results cont...
16
• Nematode densities were minimal and damage absent on
tubers intercropped with C. juncea, A. histrix, and T. erecta
2 MAS in both field and pot experiments
• Tubers intercropped with S. guianensis, P. phaseoloides,
M. pruriens and C. pubescens had slight nematode damage
• Tubers intercropped with C. cajan, L. purpureus, V.
unguiculata or no cover crop had moderate to severe
symptoms of damage.
• C. cajan, L. purpureus, and V. unguiculata supported high
nematode populations and RF in pot experiments.

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Discussion
• C. juncea, A. histrix and T. erecta were found to be
effective in managing M. incognita on yams
• Supports results of McSorley et al. (1994; 1999) and
Piedra-Buena et al. (2008)
• M. pruriens, C. pubescens, P. phaseoloides and S.
guianensis suppressed the effect of M. incognita
• Supports results of Rodriguez-Kabana et al. (1992) and
Kokalis-Burelle et al. (2005)
• L. pupureus, V. unguiculata and C. cajan were highly
susceptible to M. incognita
• Supports results of Otipa et al. 2009, Adegbite et al.,2005

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Discussion cont...
• Suppression of RKN by cover crops can be via acting as a
non-host or a poor host (Rodríguez-Kabana et al., 1992);
• Some produce allelopathic compounds that are toxic to
nematodes (Halbrendt, 1996; Wang et al., 2001)
• Stimulation of soil organisms that compete with or attack
nematodes (Hooks et al., 2010).
• D. rotundata had higher susceptibility to M. incognita
than D. alata
• M. incognita in tubers causes increased respiration of the
tuber (Fawole and Evans, 1989) which contributes to
storage weight loss.

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Conclusion
• A. histrix, T. erecta and C. juncea should be incorporated
into IPM strategies for Meloidogyne species
management
• M. pruriens, S. guianensis, C. pubescens and P.
phaseoloides were moderately susceptible to M.
incognita and may be used to reduce their Meloidogyne
species populations
• C. cajan, L. purpureus and V. unguiculata were
susceptible to M. incognita and should be avoided in
cropping systems involving susceptible crops

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