**Diseases Caused by Nematodes**

**Cyst Nematodes**

***Heterodera ciceri***

**Occurrence & Geographic Distribution**

The cyst nematode, *Heterodera ciceri,* also known as chickpea cyst
nematode, is one of the most aggressive parasites of food legumes, such
as chickpea. It was first reported to occur in Syria and was observed as
the causal agent of severe chickpea decline in the Idleb province and
other areas in the north. This nematode is distributed mainly in the
eastern Mediterranean region including Jordan, Lebanon, Syria, and
Turkey.

**Symptoms**

Small, longitudinal necrotic spots are visible on the roots of the
plant. The above-ground symptoms are early senescence, limited number of
flowers and pods, which may be empty. Lemon-shaped cyst (leathery bodies
of the adult female nematodes) can be found embedded in the roots (Fig.
1). Reduction in number of nitrogen fixing nodules has also been
observed.

> **Diagnostic Features**
>
> *Heterodera ciceri* belongs to the *H. trifolii* group but differs
> from the latter in having abundant males, different host range and
> distinct morphological characteristics. *H. ciceri* has bullae
> (irregular globose bodies below the fenestra) and longer underbridge
> than that of other members of *H. trifolii* group such as *H. fici, H.
> glycines* and *H. schachtii*. The stylet of second stage juveniles
> (J2) measures about 27-30 µm. The juveniles have four lines in lateral
> field and 3 lip annuli.

**Host ranges**

The host range is mainly confined to members of Leguminosae. The
nematode reproduces on chickpea, lentil, pea and grasspea *(Lathyrus
sativus* L.) while *Vicia* spp., bean, lupine and alfalfa are poor
hosts. However, a Syrian and a Turkish population also reproduce well on
alfalfa and *Medicago* spp. Broad bean and clovers are very poor or
non-hosts. In tests with plants in 13 botanical families, the nematode
produced a few females, only on carnation.

**Life Cycle and Epidemiology**

*Heterodera ciceri* J2 emerge from the eggs inside the cysts, migrate
through soil and penetrate chickpea roots. J2s become sedentary, swell
and complete their development by feeding on specialized stellar cells,
producing syncytium in root tissue. Swollen females rupture root tissues
and protrude from the roots surface (Fig. 2). Females do not produce egg
sacs. They retain eggs inside their bodies and may produce a gelatinous
matrix without eggs. After death, the females transform into cysts (Fig.
3), containing 200-300 eggs. On chickpea in Syria, cysts are formed
during podding stage of the plant in late spring (end of April or May)
when roots are less receptive to nematode infection and development.
Soil moisture shortage that occurs in Middle Eastern countries during
this period also suppresses nematode infection. Therefore, on these
crops, the nematode completes one generation per year. Egg hatch and
infection and development of J2 in the roots can occur at low soil
temperature (10°C) but below 8°C and above 30°C, both egg hatch and
nematode development are suppressed. Nematode development from J2 root
invasion to the appearance of cysts is attained in 36 days at 20°C.
Vermiform males develop simultaneously with the females.

Nematode eggs hatched more at 15-25°C, when stimulated by root leachates
from pea (27-33%) and from 3 mM zinc chloride solution (maximum 58%).
Although the nematode invades chickpea roots at 8°C, development only
occurs at temperatures of 10°C and above. Root invasion is suppressed at
30°C. Females may protrude a small gelatinous matrix, which is void of
eggs. In the field, large numbers of lemon-shaped white females can be
seen at the begin­ning of April or 2 weeks later on the roots of winter-
and spring-sown chickpeas, respectively. Cysts usually appear 14-16 days
later after an accumulation of 370-day degrees above the basal
temperature of 10°C.

> The tolerance limit of chickpea to *H.* *ciceri* is 1 egg/cm^3^ of
> soil. Yield losses of 20 and 50% can be expected in fields infested
> with 8 or 16 eggs of the nematode/cm^3^ of soil, respectively.
> Complete crop failure occurs in fields infested with 60 eggs/cm^3^ of
> soil. Under field conditions, severe chickpea decline can be observed
> from the end of April onwards. Infection by cyst nematodes also
> significantly reduces protein content of chickpea grain, thus lowering
> the nutri­tional value of the grain. Under poor management conditions
> the crop losses assessed under field conditions on chickpea and lentil
> may range 20-25%.
>
> The nematode generally spreads through the movement of machinery from
> one area to another. The cysts are dispersed in long distances
> adhering to the soil particles on vehicles and clothing.

**Management:** Since *H. ciceri* has a rather narrow host range, it can
be controlled effectively by crop rotation. An annual decline of 50% of
the nematode population using non-host crops has been reported.
Generally, 3-4 year rotations are effective in reducing the nematode
densities to or below the toler­ance limit. None of the nearly 10,000
chickpea lines screened showed resistance to *H*. *ciceri.* However,
resistance to the nematode was found in lines of the wild relatives, *C.
bijugum, C*. *pinnati­fidum* and *C*. *reticulatum* (Fig. 4)*.* Because
*C*. *retic­ulatum* can be crossed with C. *arietinum,* it may be
possible to produce resistant varieties of chickpea. Good nematode
control can also be obtained with a 6-8 weeks soil solarization period.

***Heterodera swarupi***

A cyst nematode, *H.* *swarupi* (Sharma *et* *a1.,* 1998) was described
from roots of chickpea in 10 districts of Rajasthan, India. The nematode
belongs to the *Heterodera schachtii* group, is close to *H*. *cajani*
and can also infect pigeonpea. The females turn yellow and produce an
egg mass with eggs. Recently, *H*. *swarupi* has been detected in
several other districts of Rajasthan, even in large numbers, but its
impact on chickpea yield has not been assessed. High populations were
found associated with poor growth of chickpea, but its economic impact
is yet to be assessed.

**Selected References**

Greco N., Di Vita M., Saxena M.C., and Reddy M.V. 1988. Effect of
*Heterodera ciceri* on yield of chickpea and lentil and development of
this nematode on chickpea. Nematologica 34: 98-114.

Greco, N. 1992. The chickpea cyst nematode, *Heterodera ciceri*.
Nematology Circular No.198, Florida Department of Agriculture and
Consumer Services, Division of Plant Industry, Gainesville, FL, USA.

Greco, N., and Di Vito, M. 1993. Selection for nematode resistance in
cool-season food legumes. Pages 157-166 in: Singh, K.B.,  Saxena, M.C. 
eds. *Breeding for stress tolerance in cool-season food legumes.* John
Wiley & Sons Ltd, Chichester, UK

Kaloshian, I., Greco, N., Saad, A. T., and Vovlas, N. 1986. Life cycle
of *Heterodera ciceri* on chickpea. Nematologia Mediterranea 14:
135-145.

Sharma, S. B., Siddiqi, M. R., Rahaman, P. F., Ali, S. S., and Ansari,
M. A. 1998. Description of *Heterodera swarupi* sp. n. (Nematoda :
Heteroderidae), a parasite of chickpea in India. International Journal
of Nematology 8: 111-116.

Sikora, R. A., and Greco, N. 1990. Nematode parasites of food legumes.
Pp. 181-235 *in:* Plant parasitic nematodes in tropical and subtropical
agriculture. M. Luc, R. A. Sikora, and J. Bridge, eds. CABI Publishing,
Wallingford, UK .

Vito, M. Di, Greco, N., Malhotra, R. S., Singh, K. B., Saxena, M. C.,
and Catalano, F. 2001. Reproduction of eight populations of *Heterodera
ciceri* on selected plant species. *Nematologia Mediterranea*. 29:
79-90.

(Prepared by H. S. Gaur, Pankaj and K. K. Kaushal)

![](media/image1.jpeg){width="1.320138888888889in" height="2.0in"}

Fig. 1. A chickpea root severely infected with many females of *H.*

*ciceri.* (Courtesy N. Greco)

![](media/image2.jpeg){width="2.0in" height="1.3798611111111112in"}

Fig. 2. Longitudinal section of a chickpea root showing a female of

*Heterodera ciceri* and several syncytial cells in central cylinder.
(Courtesy

N.Vovlas)

# 

# ![](media/image3.jpeg){width="1.2854166666666667in" height="1.9479166666666667in"}

# 

Fig. 3. White cyst formation on chickpea roots. (Courtesy ICARDA)

![](media/image4.jpeg){width="2.0in" height="1.3333333333333333in"}

Fig. 4. Disease nursery of chickpea for screening against cyst
nematodes. (Courtesy ICARDA)

**Root lesion nematodes (*Pratylenchus* spp.)**

The root lesion nematodes, *Pratylenchus* spp., are widely distributed
and have very wide host ranges. Several species of the genus are
responsible for substantial yield losses in many agriculturally
important crops. They are migratory endoparasites mostly feeding on
cells in the root cortex that results in lesions on roots and thus the
name 'root lesion nematode'.

**Occurrence and Distribution**

> The geographical distribution of the different species of
> *Pratylenchus* is mostly limited to specific areas where suitable
> temperature regimes are available. Species like, *P. coffeae*, *P.
> goodeyi*, *P. brachyurus*, *P. thornei* and *P. zeae* are commonly
> found in tropics while *P. penetrans*, *P. fallax, P. vulnus* and *P.
> crenatus* are found mainly in cooler climates. Host suitability and
> climatic factors such as soil type and its moisture levels chiefly
> govern the distribution and development of a population. More than 70
> species of the genus, *Pratylechus* have been described from different
> parts of the world.

Surveys of lesion nematodes in chickpea and lentil fields in Syria and
North Africa (Algeria, Morocco and Tunisia) revealed that the most
common nematodes encountered are *P. thornei*, *P. penetrans* and *P.
mediterraneus*. *P. thornei* is also reported as potential pest of
chickpea in Brazil, Italy, Jordan, Syria, Zimbabwe, Mediterranean
region, including southern Spain, and in the Indian subcontinent whereas
*P. penetrans* is common in North Africa. Other species known to occur
in the Mediterranean region are *P. mediterraneus, P. neglectus, P.
crenatus, P. pratensis* and *P. pinguicaudatus*, however, their impact
on chickpea production has not been assessed. In north and central India
*P. thornei* causes damage to chickpea. Both *P*. *thornei* and *P*.
*neglectus* are widespread in wheat fields in Australia, and they damage
chickpea when rotated with winter cereals.

**Symptoms and damage**

The main symptoms of root-lesion nematode in the field include stunted
growth, uneven patches or waviness across the field. Lesions or
discoloration of the roots and lack of branching along the main roots
are the main symptoms (Fig. 1). Lesions produced by these nematodes are
generally brown to black in color and run parallel to the root axis. The
lesion development varies with the plant and the species of the nematode
involved, depending upon the root cortical cell death and quantity of
the polyphenol oxidation caused by the nematode damage. These species
have the tendency to move and migrate through the cortical cells while
feeding causing visibly extensive lesions and necrosis. Their habit of
migrating from cell to cell, in and out of the root, making entry points
thus, facilitates the attack by the secondary invaders. Heavily infected
roots are reduced in size and usually are devoid of or have stunted
rootlets. Such root dysfunctions result in stunted, patchy and chlorotic
growth of above ground plant parts.

Damage to plants depends on nematode density in the soil. Studies in
India have shown that population densities ≥0.1/g of soil were
responsible for significant growth reduction, while densities of ≥4/g of
soil also reduced germination. Under field conditions in Syria, the
tolerance limit of chickpea to the nematodes was 0.03 nematode/cm^3^ of
soil, with yield loss of 58% at 2 nematodes/cm^3^ of soil. Yield losses
of 25 and 75% in winter- and spring-sown chickpea, respectively, were
observed in fields infested with *P. thornei.* The nematode is also
known to adversely affect root nodulation by *Rhizobium*.

In soil infested with *P. thornei*, grain yield losses up to 20% have
been reported. *P.* *neglectus* can cause yield losses greater than 20%
in intolerant crops. Surveys showed that high populations were present
in some soils associated with a broad range of cropping programs.
However, wheat and chickpeas were implicated as the most significant
contributors to population increases of lesion nematodes.

**Identifying features**

The lesion nematodes are small to medium sized, stout and having body
length usually less than 0.9 mm with no sexual dimorphism. All the
juvenile stages, males and females are vermiform. Head is low and flat,
sclerotized, continuous; sometimes setoff, with two, three or
occasionally four labial annuli. Lateral field is marked by 4-6
incisures. Stylet is short (20 µm or less) but stout, heavily
sclerotized with round, flat and anteriorly projected knobs. Dorsal
oesophageal gland opening is just behind the stylet knobs and ventral
overlap of intestine is short, 2-3 body width long. Vulva at 70-88% of
body length with posterior branch reduced as post-uterine sac. Female
tail is cylindrical to conoid usually 2-3 anal width long. Phasmids are
placed mid tail or may be a little posterior. Bursa is peloderan
enclosing the tail tip. Spicules are moderate and gubernaculum is
simple, trough- like and fixed.

**Host Range**

The lesion nematodes can easily reproduce on a wide host range plants
that serve as good hosts for some species in the genus. *P. penetrans*
and *P. coffeae* have more than 350 and 130 known hosts, respectively.
The host ranges of *P. neglectus* and *P. thornei* includes most cereals
and potential rotation crops such as grain legumes, pasture legumes, and
oilseeds. Minimal reproduction of *P. neglectus* and *P. thornei* occurs
on pea and safflower, reducing the level of risk for subsequent crops.
Reproductive rates are high on many chickpea varieties, amplifying the
risk to subsequent crops. *P. neglectus* reproduces very well on most
varieties of canola, mustard and lentil. *P. thornei* reproduces at
significantly lower rates on these crops. Reproduction of both species
is generally greater on wheat than on barley but large differences occur
among varieties of both crops. In South Africa, lentils are classified
as resistant to both *P. neglectus* and *P. thornei,* based on screening
trials conducted prior to 2002, which included the following varieties
and lines: Ansak, Cassab, Cobber, Cumra, Digger, ILL61, Laird, Matilda,
Northfield, Nuggett and Spinner.

**Life Cycle and Epidemiology**

Root lesion nematodes can be found free in soil. The II, III and IV
stage juveniles and adult females feed on root cortical tissues,
creating tunnels in root cortex. This tunneling progresses as the
nematodes migrate from one cell to another. Eggs are laid singly but
only two per day or in clusters due to the gregarious nature of the
lesion nematodes, both, in soil along the root surface and in the root
tissues. Second stage juveniles (J2s) hatch after eggs have incubated
for 9 (at 30^o^C) to 25 (at 15^o^C) days. As the nematode develops in
the egg, it molts to change from a first stage juvenile to a J2, which
then hatches from the egg. Probably no hatching stimulus is required,
but adverse soil conditions such as drought and extreme temperatures
inhibit or delay hatch. The juvenile nematodes sometimes feed
ectoparasitically on plant root hairs but more specifically they enter
into the root cortex and live there. These entry points make the way for
many nematodes to enter resulting in clusters within the root tissue.
The nematodes pierce the cell wall by repeated thrusts and pause there
to feed. While feeding they secrete salivary enzymes, which help in
ingesting the cytoplasm. The inter- and /or intra-cellular migration of
nematodes results in the cell death. They grow and molt three more times
to become mature males or females. Males are very rare in some species,
and females of these species have parthenogenetic type of reproduction.
Males are required for reproduction by *P. penetrans* but not by *P.
neglectus*. They are multivoltine with more than one generation per
season and are able to migrate between and within the roots and soil.
These nematodes survive over summer in a dehydrated state, becoming
active again once moisture is available. The drying root tissues slow
the rate of water loss from nematode body, thus improving the chance of
anhydrobiotic survival. The duration of life cycle under optimum
temperature around 25^o^C is about one month, but it can be longer, up
to 2 months, at lower or higher temperature. Peak population densities
are attained a few weeks before harvest, in the end of March in India.

**Interaction with other pathogens**: The cortical cells are prone to
attack of other soil microbes, which in presence of nematode increases
the severity of damage manifold. The invasion of *Rhizoctonia
bataticola* (*Macrophomina phaseolina*) and *P. thornei* in chickpea
roots causes destruction of epidermal cells. *P. thornei* penetrated the
roots directly and *R. bataticola* was thought to secrete macerating
enzymes. Plant growth was significantly reduced by *P. thornei*
infection on wilt-susceptible and wilt-resistant chickpeas in controlled
and field conditions, except when shorter periods of incubation (45 d
after inoculation) were used under controlled conditions. Both *F.
oxysporum* f. sp. *ciceris* and *P. thornei* are also widely distributed
throughout the major chickpea production areas of the world.

**Management**

Specific management measures have not been developed for lesion
nematodes on chickpea. Most species of *Pratylenchus* have wide host
ranges; therefore, control by rotation is not very effective. This is
espe­cially true in rotations with winter cereals, which are often good
hosts for the lesion nematodes. However, rotation of cool season with
warm season crops would be a satis­factory approach to control *P.
thornei.* Summer plowed plots recorded significantly higher crop yield
and lower soil and root population of *P. thornei* than the control.
Summer plowing combined with 0.1% carbosulfan seed soaking significantly
reduced the final soil and root population of *P. thornei*. Seed soaked
in 0.1% carbosulfan when sown in plots without summer plowing exhibited
significantly lower soil and root population and 40% increase in yield
than the rest of the treatments including the control.

Soil amendments with various deoiled cakes (pomace) of groundnut,
mustard, linseed and neem reduced the nematode population and also
increased the yield of chickpea. Groundnut and mustard cakes are,
however, more useful as cattle-feed. Although chemical control is not an
economically acceptable management measure, it has been demonstrated
that split applications of aldicarb at 10 kg a.i./ha at sowing and after
seed germina­tion can control *P*. *thornei* and increase yield. Seed
treatment with aldicarb, carbofuran and fensulfoth­ion gave satisfactory
control of the nema­tode in pot tests. The application of aldicarb,
carbofuran, fensulfothion or phorate at 3 doses (1 to 2% a.i. seed
weight) each to chickpea through seed treatment significantly reduced
final populations of *P. thornei*, the highest doses giving the greatest
nematode reduction. Phorate gave better control of *P. thornei* than
carbofuran (both at 2 kg a.i./ha) on chickpeas in experimental plots.
The application of carbofuran, fensulfothion or phorate at 3 doses (1 %
a.i. seed weight) each to lentil through seed treatment significantly
reduced final populations of *P. thornei*, the highest doses giving the
greatest nematode reduction.

The reaction of chickpea cultivars may differ, and some can be tol­erant.
*P. thornei* appears to reproduce well on cool season crops and poorly
on warm season crops. The soil populations were greatly reduced in
solarized plots and nematode numbers were also reduced in chickpea roots
collected in mid April. Soil solarization using polyethylene mulch
during May-June for 6-8 weeks significantly decreases nematode
population. Even placing poultry litter prior to solarization is also
effective in reducing the nematode. Improved fertility of soil increases
the ability of crops to tolerate damage.

Early sowing minimizes yield losses in spring sown lentil, while reverse
may be true in the autumn sown crops in the subtropics with distinct
winter and summer as in northern India. Lower soil temperature, 15-20°C
reduces nematode movement and root invasion.

A suitable chickpea cultivar with resistance to nematodes is not
available. Therefore, investigations are required to enable development
of crop management strategies that can be utilized to maintain nematode
populations below threshold levels. However, resistance to *P. thornei*
was reported in several lines and accessions of cultivated and wild
chick­peas, *Cicer reticulatum*. Sources of nematode resistance in
chickpea need to be identified for use in future breeding programs.
Chickpea lines GNG 543, GF 88428 and PKG-24 were rated as highly
resistant to *P. thornei* in pot tests in India.

**References**

Bhatt, J., and Vadhera, I. 1997. Histopathological studies on
cohabitation of *Pratylenchus thornei* and *Rhizoctonia bataticola* on
chickpea (*Cicer arietinum* L.). Advances in Plant Sciences 10: 33-37.

Castillo, P., Mora-Rodriguez, M. P., Navas-Cortes, J. A., and
Jimenez-Diaz, R. M. 1998. Interactions of *Pratylenchus thornei* and
*Fusarium oxysporum* f.sp. *ciceris* on chickpea. Phytopathology 88:
828-836.

Castillo, P., Trapero-Casa, J. L., and Jimenez-Diaz, R. M. 1996. The
effect of temperature on hatching and penetration of chickpea roots by
*Pratylenchus thornei.* Plant Pathology 45: 310-315.

Loof, P. A. A. 1991. The family Pratylenchidae Thorne, 1949. Pages
363--421 in: *Manual of Agricultural Nematology*, W.R. Nickle ed.,
Marcel Decker, New York.

Sebastian, S., and Gupta, P. 1997. Crop loss trial of chickpea infested
with *Pratylenchus thornei.* Indian Journal of Nematology 27: 142-143.

Vito, M. di, Catalano, F., and Zaccheo, G. 2002. Reproduction of six
populations of *Pratylenchus* spp. from the Mediterranean region on
selected plant species. Nematologia Mediterranea 30:103-105.

Vito, M. di, and Greco, N. 1994. Control of food legume nematodes in the
Mediterranean Basin. Bulletin OEPP 24: 489-494.

Vito, M. di, Greco, N., Oreste, G., Saxena, M. C., Singh, K. B., and
Kusmenoglu, I. 1994. Plant parasitic nematodes of legumes in Turkey.
Nematologia Mediterranea 22: 245-251.

(Prepared by: H. S.Gaur, Pankaj and K. K. Kaushal)

![](media/image5.png){width="3.499212598425197in"
height="1.999212598425197in"}

Fig. 1. Root-lesion nematode damage to chickpea roots (Photo: Courtesy
AICRP, Nematodes)

**Reniform Nematode (***Rotylenchulus reniformis*)

**Occurrence and Distribution**

There are ten species of the genus *Rotylenchulus*. *Rotylenchulus
reniformis* and *R. parvus* are known to infect chickpea, the former
being widespread. *R. reniformis* is known to occur practically
everywhere in tropical and subtropical soils. It exists in the
Caribbean, Mexico, South America, the Middle East, most of Africa,
Pakistan, India, South East Asia, China, Japan, Australia and the
Pacific islands. *Rotylenchulus reniformis* also infects lentil in
India, Pakistan and other countries.

**Symptoms and damage**

General symptoms in the field are patches of stunted chlorotic plants.
Infected plants generally grow less vigorously than healthy ones and
their roots appear dirty because of soil particles sticking to nematode
egg sacs. The amount and type of damage by *R. reniformis* depends on
host and/or cultivar as well as the nematode population. Leaf chlorosis,
overall stunting, reduced branching and longevity of plants and reduced
yields are noticed. Female nematodes and their eggs are often visible
when plant roots are viewed under a dissecting microscope.

**Causal Organism**

The term \'reniform\' refers to the kidney-shaped body of the mature
female. The nematode is semi-endoparasitic (partially inside roots) in
which the females penetrate the root cortex, establish a permanent
feeding site in the pericycle region of the root and become sedentary.
If the infected roots are dipped in 0.25% trypan blue and rinsed in
water, the nematode egg sacs are selectively colored blue while plant
roots are not stained.

**Identifying Features**

The average body length of *R. reniformis* is about 0.35 to 0.45 mm for
juveniles and males, and 0.38 to 0.52 mm for mature female nematodes.
The juveniles, young females and males attain C shape when killed by
gentle heat. The lip region of the young female is not offset, and the
cephalic framework is conspicuous. The stylet, 16 to 21 µm long, is of
moderate strength with small rounded knobs. The dorsal gland orifice is
more than one-half the stylet length posterior to the base of stylet
knobs. The basal glands overlap the intestine laterally, or less often
ventrally. The vulva is post-median (V\>63%). The female reproductive
system is amphidelphic with two flexures in immature females and highly
convoluted in kidney shaped mature females (Fig-1). The female tail is
usually more than twice the anal body diameter. The juvenile tail tapers
to a narrow, rounded terminus with about 20 to 24 annules. Phasmids are
porelike, about the body width or less behind anus. Males have weak
stylet and stylet knobs, a reduced esophagus, and an indistinct median
bulb and valve. Bursa is small and adanal.

**Host range**

At least 314 plant species are host to reniform nematodes. *R.
reniformis* parasitizes a large number of cultivated plants and fruit
trees throughout tropical and subtropical areas. It is known to affect
*Allium*, pineapple, begonia, beet, bougainvillea, broccoli and
cauliflower, cabbage, pigeon pea, papaya, chrysanthemum, watermelon,
cucumber, winter squash, carrot, whiter ginger, okra, garden balsam,
lettuce, tomato, bitter gourd, banana, passion fruit, wild bean, lima
bean, garden bean, chickpea, lentil, pea, tuberose, radish, eggplant,
black nightshade, potato, *Sorghum caudatum,* marigold, cowpea, corn,
coffee, taro, citrus, ginger and *Xanthosoma* spp..

**Life Cycle and Epidemiology**

These nematodes have a unique life cycle. The development up to adult
male and female occurs without feeding. Only the young female reniform
nematode parasitizes plant roots. It imbeds its head into root tissue
while the tail end remains in the soil (Fig. 1). Nurse cells (100-200
per female) form near pericycle. Feeding causes hypertrophy of pericycle
and endodermis cells, increased cytoplasm density, but cells remain
uninucleate with large nucleolus. *R. reniformis* generally remains in
the first 15 cm of soil. Distribution is irregular and is greatest in or
around roots of susceptible plants. Nematodes sometimes follow roots to
considerable depths (30 to 150 cm or more). As it feeds and grows, the
posterior end enlarges, gradually attaining a kidney or bean shape. A
gelatinous matrix is secreted through vulva. The female deposits 50 -
200 eggs into the gelatinous matrix, seven to nine days after infecting
the root (Fig. 2). Eggs hatch in 8-10 days. A nematode goes through four
molts before becoming an adult. The first molt occurs within the egg and
the second stage juvenile hatches and molts three times successively.
Nematodes differentiate into adult males and females after the fourth
molt. The molted cuticular sheaths are retained until the adult male and
female start moving. This complete life cycle (Fig. 3) takes 24 to 29
days at optimum conditions. Males have a poorly developed stylet and
esophagus for feeding. The young female is vermiform and has an immature
reproductive system. Males are strongly attracted to the females.  There
is a 1:1 sex ratio. Some populations have few or no males.

In drying soil the young females and males undergo anhydrobiosis. The
molted culticular sheaths help in reducing the rate of water loss during
desiccation. The nematode also coils to reduce the exposed surface area.
In this state the reniform nematodes can survive for more than three
years.

The nematodes move slowly in soil pore spaces but dispersal is mainly
passive. They can be easily transported by anything that moves or
carries soil particles. Farm equipment, irrigation, flood or drainage
water, animals (including humans), and dust storms spread nematodes in
local areas, while over long distances nematodes are spread primarily
with farm produce and nursery plants.

**Management**

Although the host range is vast, a number of susceptible crops have
resistant or somewhat resistant cultivars to the reniform nematode.
Rotation with cereals can reduce population densities. Rotation with
corn, sorghum, and wheat reduced populations of reniform nematode.
Plantings of poor host species can reduce the reniform nematode numbers
in soil more effectively than fallow alone. Non-host crops included
marigold (*Tagetes patula* L. and *T. erecta* L.), sunn hemp
(*Crotalaria juncea* L.), rhodes grass (*Chloris gayana* Kunth), and
pangola grass (*Digitaria decumberns* Sent.). Traditionally in India,
chickpea is cultivated in rotation with crops like pearl millet,
sorghum, maize that do not promote buildup of reniform nematodes. But
many weeds may sustain their population densities.

Soil solarization using polyethylene during summer months decreases
population densities and increase yield but it may not be economical in
chickpea. The effect of solarization does not last beyond one crop
season and may or may not last through harvest. Summer plowing reduces
population densities.

Soil amendments such as animal manure and oilseed cakes have been used
with success to control the reniform nematode, but large amounts need to
be applied. Oil seed cakes of neem/margosa (*Azadirachta indica*),
castor (*Ricinum communis*), cotton, mustard (*Brassica compestris*),
rocket salad/duan (*Eruca sativa*) were found to be highly effective in
reducing the multiplication of nematodes and consequently plant growth
and bulk density increased significantly. Damage caused by the nematodes
was further reduced when *Paecilomyces lilacinus* was added along with
oil cakes. Most effective combination of *P. lilacinus* was with neem
cake.

**Selected References**

Gaur, H. S., and Perry, R. N. 1991. The biology and control of the plant
parasitic nematode, *Rotylenchulus reniformis.* Agric. Zool. Rev*.* 4:
177-212.

Gaur, H. S., and Perry, R. N. 1991. The use of soil solarization for
control of plant parasitic nematodes. *Nematological Abstracts* 60:
153-167.

Heald, C. M., and Inserra, R. N. 1988. Effect of temperature on
infection and survival of *Rotylenchulus reniformis*. J. Nematology 20:
356-361.

Heald, C. M., and Robinson, A. F. 1987. Effects of soil solarization on
*Rotylenchulus reniformis* in the lower Rio Grande Valley of Texas. J.
Nematology 19: 93-103.

Robinson, A. F., Inserra, R. N., Caswell-Chen, E. P., Vovlas, N., and
Troccoli, A. 1997. *Rotylenchulus* species: Identification,
distribution, host ranges, and crop plant resistance. Nematropica 27:
127-180.

Sharma, S. B., and Nene, Y. L. 1990. Effects of soil solarization on
nematodes parasitic to chickpea and pigeonpea. *J. Nematology* 22:
658-664.

(Prepared by H. S. Gaur, Pankaj and K. K. Kaushal)

![](media/image7.jpeg){width="2.975in" height="4.618055555555555in"}

Fig. 1. Females (different stages, stained) of *Rotylenchulus
reniformis* feeding on root. (Courtesy H.S. Gaur)

![](media/image8.jpeg){width="4.50625in" height="3.098611111111111in"}

Fig. 2. Egg sacs (stained broken to show eggs) of *Rotylenchulus
reniformis* on chickpea root. (Courtesy H.S. Gaur)

![](media/image9.png){width="4.5125in" height="2.970138888888889in"}

Fig. 3. Life cycle of *Rotylenchulus reniformis.* Note egg sac, eggs,
juvenile, male and females. (Courtesy H.S. Gaur)

# Root-knot nematodes (*Meloidogyne* spp.)

Root-knot nematodes, *Meloidogyne* spp., are the most widely prevalent
and economically the most important group of plant parasitic nematodes.
They are sedentary endoparasites of a vast range of plants, including
many cultivated vegetable, pulse, fruit, cereal, fiber, fodder, oilseed,
ornamental, spices and other types of crops. There are about 100 species
of *Meloidogyne*, most have wide host ranges, but a few are limited to
either monocot or dicot crops. *Meloidogyne incognita*, *M. javanica*,
*M. arenaria*, *M. hapla* and *M. graminicola* are the most widespread
species; the first three infect chickpea and lentil. A few other species
infecting these crops are localized in distribution.

## Occurrence and Distribution

About 24 root-knot species belonging to the genus *Meloidogyne* are
prevalent in Asian countries infecting a variety of hosts. They pose
serious constraint in cultivation of chickpea and lentil, mainly in
tropical, sub-tropical and some temperate regions of the world. These
nematodes have been reported damaging chickpea in Bangladesh, Brazil,
Egypt, Ethiopia, Ghana, India, Malawi, Nepal, Pakistan, Spain, Syria,
Sudan, Turkey, USA, Zambia and Zimbabwe. *M. incognita, M. javanica* and
*M. arenaria* are the major nematode pests on chickpea in Indian
sub-continent. *M. artiellia* has been reported to occur in diverse
agro-climates such as Algeria, England, France, Greece, Italy, Israel,
Morocco, Spain, Syria, Tunisia and western Siberia. It infects and
damages a wide range of crops including cereals, crucifers and legumes.
In the Mediterranean region, *M. artiellia* is a pest of chickpea
capable of causing yield losses up to 80% in addition to the damage
caused by *M. incognita* and *M. javanica.*

## Symptoms and damage

The infected plants of chickpea have usually excessively branched roots
with large galls, which may later on rot due to the secondary infection
by other microorganisms. The infested plants are generally stunted with
chlorotic foliage, which flower poorly (Fig. 1-6). Such plants bear few
and smaller pods that are often empty and the root system is also
reduced. The combined population of *M. incognita* and *M. javanica*
usually enhances the severity of the *Fusarium oxysporum* f.sp.
*ciceri*. Also the chickpea varieties may lose their resistance to
fungal pathogens when infested with the root-knot nematode. Under heavy
infestation regimes the nematode may also develop on Rhizobium nodules.
The longevity and nitrogen fixing ability of Rhizobium nodules is
reduced. The damage has been recorded to be many fold if the crop of
chickpea is grown in sandy loam soils*. M. arenaria* is prevalent in
Ghana and *M. javanica* in the Ethiopian highland. Like chickpea, lentil
is also threatened by these root-knot nematodes and reports of damage
caused by *M. incognita* and *M. javanica* in India and by *M incognita*
in Pakistan are found in literature. The galls produced by *M. artiella*
are less conspicuous but many egg sacs can be seen protruding from the
root surface (Fig. 7).

### Identifying features

Many of the *Meloidogyne* species are easily identified. The pyriform
body shape, 0.5-1.0 mm in diameter, is typical for most species and the
neck and perineal region are in line with the longitudinal axes. The
most characteristic feature of females of most *Meloidogyne* species is
the perineal pattern in the posterior body region. The globose females
are mostly embedded in the roots with their vulval region outside the
roots for laying eggs in the gelatinous matrix. Female cuticle is white,
thin and annulated. Labial portion is weakly sclerotized. Stylet is
short. Excretory pore is located in the region of medium bulb, which is
greatly muscularized. The body is filled with two convoluted genital
tracts.

In addition to the perineal pattern characters, the shapes of the male
head and stylet are extremely useful characters in the identification of
*Meloidogyne* species. Isozyme phenotypes especially esterase and malate
dehydrogenase mobility, have been found useful in differentiating some
species. The DNA-based nematode identification techniques have been
utilized to differentiate the species and morphologically similar host
races or pathotypes with great accuracy. Restriction Fragment Length
Polymorphism (RFLP), DNA hybridization dot blots, DNA sequencing of
internal transcriber spacers (ITS) of rDNA or mtDNA and Randomly
Amplified Polymorphic DNA (RAPD) analysis have been developed for
root-knot and other nematodes.

**Life cycle and Epidemiology**

The life cycle of the *M. incognita* and *M. javanica* takes less than a
month to complete at optimum temperature around 28^o^C, but may extend
up to 75 days at suboptimal temperatures. It undergoes six stages: egg
stage, first and second juvenile stage within the egg, free second-stage
juveniles in soil, three juvenile stages (J2, J3 and J4) in plant
tissue, adult female in plant tissue (Fig. 8) and adult male moving
freely in soil or trapped in egg sac.

Second-stage juveniles, found free in soil or moving from one site to
another within plant tissues, are infective. They penetrate the root in
the elongation zone and orient their tails towards root tip. They
continue to move inter- and intra-cellularly until they reach the
vascular bundles and become sedentary. The secretions from the dorsal
esophageal glands are injected into host plant cells inducing
enlargement of cells near the head with multinucleate conditions.
Karyokinesis (division of the cell nuclei) occurs without cytokinesis
(division of cells). The large multinucleate cells, the syncytium, are
called giant cells or nutrient sink cells. Female root-knot nematodes
mostly reproduce parthenogenetically. More males are formed in response
to stress.  Multiplication and hypertrophy of cells takes place in the
epidermal tissue resulting in the gall formation at the feeding site.
Sometimes multiple galling may occur due to the feeding of more than one
female at the adjacent cells. Even the J2 normally destined to produce
females may develop into males when there is overcrowding, scarcity of
food or high soil temperature. Mature females are saccate (pear-shaped)
and lay eggs into a gelatinous matrix. This matrix protrudes from the
surface of roots or may be entirely within the gall. Eggs hatch in about
7 days. The eggs may hatch soon, thus, starting the second generation
and in this way many generations are produced during one crop season.

*Meloidogyne artiellia* reproduces best at 20-25 ^o^C, whereas *M.
incognita* and *M. javanica* multiply best at 25-30^o^C. Generally, the
gall size is influenced by the host variety and soil texture and
temperature. Large sized galls are produced at 25-30^o^C than at lower
temperatures of 10-20^o^C in these two nematodes. In *M. artiellia*, the
galls formed are smaller and sometimes even not visible to naked eye,
but egg masses are clearly seen as manifestation of its infection.

The juveniles are abundant in the upper 20 cm layer of the field soil
but the vertical distribution may be influenced by soil temperature and
moisture. Under high moisture stress the populations are relatively
higher in deeper layers, perhaps due to differential rates of hatching
or the survival in different layers. The egg sac produced by the female
becomes brown and may contain several hundred eggs. Eggs hatch without
requiring host diffusate but the rate of hatch is increased in the
presence of host root diffusates; the second stage juveniles invade
roots and migrate to the site of differentiating vascular tissues where
they feed and induce the development of several giant cells around the
nematode head. This leads to the formation of galls.

Soil tem­peratures suitable for nematode attack and development are not
reached until late spring, allowing the plant to escape the damaging
early root invasion process. For this reason, root-knot nematodes,
although important on other summer crops, do not constitute a problem on
chickpea in the Mediterranean basin. Most nematodes are spread through
free-flowing water or contaminated machinery. Because of this, infected
plants are aggregated (or spread in the direction of tillage or
irrigation furrows) instead of evenly distributed.

One to two juveniles of *M. incognita* per gram of soil are usually the
economic threshold level, although it depends upon plant
species/variety, soil and several environmental factors prevailing
during the growing season and disease complexes.

During the dry season these nematodes survive in egg stage or as
anhydrobiotic second-stage juveniles in the soil. Crop may be devastated
if the initial inoculum level exceeds one egg or juvenile per cm^3^ of
soil. Spring chickpea has been observed to be more susceptible than the
winter grown crop. The infection by these nematodes has adverse effect
on formation of rhizobial nodulation. The nodules may also be infected.
Reduction in the longevity and leghaemoglobin content of nodules has
been reported on cowpea.

**Interaction with other pathogens:** Pathogenic fungi such as *Fusarium
oxysporum* and *Rhizoctonia solani* more easily colonize roots infected
by root-knot nematodes. Role of root-knot nematodes in the chickpea wilt
complex has been established. Chickpea varieties lose their resistance
to the fungus when infested with root-knot nematode. In chickpea
genotypes with complete resistance to Fusarium wilt, infection by *M.
artiellia* overcame the resistance to *F oxysporum* f. sp. *ciceris*
race 5 in CA 334.20.4 and CA 336.14.3.0 but not in ICC 14216 K,
irrespective of the fungal inoculum density, and overcame the resistance
in UC 27 only at the higher inoculum density. Infection by the nematode
significantly increased the number of propagules of *F. oxysporum* f.
sp. *ciceris* Race 5 in root tissues of genotypes with complete
resistance to Fusarium wilt, compared with roots that were not
inoculated with the nematode, irrespective of the fungal inoculum
density.

#### Management

Implementation of effective crop rotation for the control of
*Meloidogyne* spp. becomes difficult because of their wide host range.
Rotation schemes including fallow are used to control root-knot on
chickpea. Crop rotation with cereal crops \\such as wheat, barley or
pearl millet or mustard may reduce the population, as these crops are
poor hosts of *M. incognita* and *M. javanica.* In parts of India where
chickpea is grown in rotation or as intercrop with cereals, root-knot
nematodes have not been found to be a problem. Many weeds have been
reported to be excellent hosts for root-knot nematodes; therefore, good
weed control is important to a rotation program under both non-host and
fallow conditions.

The damage is more prominent in the subtropical semi-arid Mediterranean
basin, where chickpeas are planted in sandy-loam soils in late summer or
early autumn. Crop injury is mini­mized when chickpeas are sown from late
autumn into the winter season. Sowing in late autumn, when soil
tem­perature drops below 18°C, and harvesting in spring can limit or
prevent nematode reproduction*.* Postponing sowing of chickpea to late
autumn has also been shown to suppress yield loss in India*.*

Cover/trap crops and antagonistic plants reduce nematode populations as
well as conserve soil and improve its texture. In localities where land
availability permits the use of cover crops, especially plants that
serve as trap crops or offer other suppressive effects on nematode
populations, should be considered.

The deoiled oil cakes (pomace) of neem (*Azadirachta indica*), linseed
(*Linum usitatissimum*), *mahua* (*Madhuca indica*), *karanj* (*Pongamia
glabra*) and sawdust reduce root-knot nematode populations, increase
soil fertility and also improve soil structure. Addition of neem
cake/decomposed neem seed was more effective than *karanj* cake. The use
of these amendments in the field is not practical on a large scale
because of poor farmer access to the mater­ial, costs of transport, or
the large quantity required for promising nematode control.

Integration of different management practices is considered to be a
better option compared to an individual approach. Integration of soil
solarization (for 6 weeks), vesicular arbuscular mycorrhiza fungus
*Glomus fasciculatum* inoculation and seed treatment with carbosulfan
(3% w/w) are highly effective in reducing population levels of *M.
incognita* and *F. oxysporum* and significantly increasing chickpea
grain yield. Seed treatment with carbendazim (0.25% w/w) together with
carbosulfan (3% w/w) is effective in reducing the *Fusarium-Meloidogyne*
wilt complex and increasing the yields. Combination of seed treatments,
summer plowing, cropping systems, use of resistant cultivars and other
physical and chemical control measures need to be stressed.

A few fungi (*Trichoderma viride*, *T. harzianum*) and bacteria
(*Pasteuria penetrans*) are potential biocontrol agents for *M.
incognita*. The major limitation in biological control is the bulk
production, storage and distribution of bio-agents for large scale
application in the field. Secondly, the soil environment is a
well-buffered system, which is difficult to modify for long periods.
*Paecilomyces lilacinus* at 2 g per pot has been reported to control *M.
javanica* when used one week before nematode inoculation. The number of
spores of *Pasteuria penetrans* at 30 per juvenile of *M. javanica*
provided more than 80% control of nematode in chickpea. *Paecilomyces
lilacinus* and *Bacillus subtilis* have been used as biocontrol for *M.
incognita* race 3*.* The use of bio-agents is presently feasible for
nursery bed treatment or for treatment of seeds. The organic amendment
and *T. harzianum* increased the chickpea growth over the control.
Combined use of *Pseudomonas fluorescens* with *Glomus mosseae* was
better at improving plant growth and reducing galling and nematode
multiplication than any other combined treatment. Soil treatment with
several nematode antagonistic fungi and mycorrhizae has given promising
results under controlled conditions, as did seed coating with
nematicides, nematicidal-active plant extracts, fungus filtrates and
rhizobacteria, alone or in combination with other control means.

**Selected References**

Ali, S. S., and Sharma, S. B. 2003. Nematode survey of chickpea areas in
Rajasthan, India. Nematologia Mediterranea 31: 147-149.

Ali, S. S., and Askary, T. H. 2001. Taxonomic status of phytonematodes
associated with pulse crops. Current Nematology 12: 75-84.

Gaur, H. S., Mishra, S. D., and Sud, U. C. 1979. Effect of date of
sowing on the relation between the population density of the root-knot
nematode, *Meloidogyne incognita* and the growth of three varieties of
chickpea, *Cicer arietinum.* Indian Journal of Nematology 9: 152-159.

Greco, N., and Sharma, S. B. 1990. Progress and problems in the
management of nematode diseases. Pages 135-137 in: Chickpea in the
nineties: Proceedings of the Second International Workshop on Chickpea
Improvement*.* ICRISAT Center, India. ICRISAT, Patancheru, A.P. 502 324,
India.

Mishra, S. D., and Gaur, H. S. 1979. Effect of planting schedule on the
population density of *Meloidogyne incognita* and the growth of *Lens
culinaris.* Bulletin of Entomology 20: 71-74.

Sikora, R. A., Greco, N., and Silva, J. F. V. 2005. Nematode parasites
of food legumes. Pages 259-318 in: Plant Parasitic Nematodes in
Subtropical and Tropical Agriculture*,* M. Luc, R. A. Sikora and J.
Bridge, eds. CABI Publishing, Wallingford, UK .

(Prepared by H. S. Gaur, Pankaj and K. K. Kaushal)

![](media/image10.jpeg){width="2.33125in" height="4.878472222222222in"}

Fig. 1. Lentil plant infected by *Meloidogyne incognita* (Courtesy S.S.
Ali and B. Singh)

![](media/image11.png){width="3.0034722222222223in"
height="2.326388888888889in"}

Fig. 2. Enlarged view of galls on roots of lentil caused by *Meloidogyne
incognita* (Courtesy S.S. Ali and B. Singh)

![](media/image12.jpeg){width="3.629861111111111in" height="2.04375in"}

Fig. 3. Patches with plants killed by root-knot nematode and root-rot
fungus disease complex (Courtesy H.S. Gaur)

![](media/image13.jpeg){width="2.4402777777777778in" height="4.0in"}

Fig. 4. Chickpea roots with galling due to *Meloidogyne incognita*
(Courtesy AICRP, Nematodes)

![](media/image14.jpeg){width="2.145138888888889in"
height="3.245833333333333in"}

Fig. 5. Severe galling of chickpea roots due to *Meloidogyne javanica*
(Courtesy AICRP, Nematodes, IARI, New Delhi)

![](media/image15.jpeg){width="3.0in" height="2.0930555555555554in"}

Fig. 6. Several large egg masses of the root-knot nematode *Meloidogyne*

*artiellia* on the root of chickpea. Note the near absence of galls
caused

by the nematode. (Courtesy N. Greco)

![](media/image16.jpeg){width="2.920138888888889in"
height="2.3666666666666667in"}![](media/image17.jpeg){width="3.0in"
height="2.2465277777777777in"}

Fig. 7. A. *Meloidogyne* females dissected out of a gall on a root.
(Courtesy AICRP Nematodes, IARI,New Delhi) , B. *Meloidogyne incognita*
female (Courtesy S. Ganguly)

**Stem Nematodes: *Ditylenchus dipsaci***

**Occurrence and geographical distribution**

Stem nematode *Ditylenchus dipsaci* is primarily distributed in most of
the temperate areas of the world (Europe and the Mediterranean region,
North and South America, northern and southern Africa, Asia and
Oceania). It does not seem able to establish itself in tropical regions
except at higher altitudes that have a temperate climate. In most
countries regulatory measures (e.g. phytosanitary certification schemes)
are applied to minimize further spread of *D. dipsaci*.

**Symptoms and Crop Damage**

*Ditylenchus dipsaci* was found associated with lentil crop in Syria
where the base of stems showed brownish necrotic lesions. Symptoms have
been more apparent in other crops. *D. dipsaci* is a migratory
endoparasite that feeds on parenchymatous tissue in stems as well as
bulbs, causing the breakdown of the middle lamellae of cell walls.
Feeding of nematode causes swellings and distortion of aerial parts of
plant (stems, leaves, flowers) and necrosis or rotting of stem bases,
bulbs, tubers and rhizomes. During cold storage of bulbs and tubers, *D.
dipsaci* and rotting may continue to develop. Crop damage to lentil has
not been measured but if late winters and early spring remain cool and
moist the crop may suffer.

**Diagnostic Features**

All juvenile stages, female and male are vermiform; body is straight
when relaxed.  Lateral field has four incisures.  Head is unstriated,
continuous with adjacent body part.  Stylet cone is about half of stylet
length with knobs rounded.  Median esophageal bulb is muscular, with
thickenings of lumen walls about 4-5 µm long.  Basal bulb is offset or
overlapping intestine for a few micrometers.  Excretory pore is opposite
the posterior part of the isthmus or glandular bulb.  Postvulval part of
uterine sac is about half of vulva-anus distance long or slightly more. 
Male cloacal alae envelop about three-quarters of tail length.  Spicules
are 23-28 µm long.  Tail of both sexes is conical, always pointed.

**Host Range**

This nematode is known to attack over 450 different plant species,
including many weeds. However, it occurs in more than ten biological
"races" some of which have a limited host-range. The race(s) that breed
on rye, oats and onions seem to be polyphagous and can also infest other
crops, whereas those breeding on alfalfa, *Trifolium pratense* and
strawberries are virtually specific for their named hosts and have
relatively few alternative hosts. The tulip race also infects
*Narcissus*, whereas another race commonly found on *Narcissus* does not
reproduce on tulip. It is known that some of the races can interbreed
and that their progeny have different host preferences. The principal
hosts are faba beans, garlic, *Hyacinthus orientalis*, leeks, alfalfa,
maize, *Narcissus,* oats, onions, peas, *Phlox drummondii*, *P.
paniculata*, potatoes, rye, strawberries, sugarbeet, tobacco, *T.
pratense*, *T. repens* and tulips. It has also been reported on
carnations, celery, *Hydrangea*, lentils, rape, parsley, sunflowers and
wheat.

In heavy infestation crop losses of 60-80% are not unusual. Transport of
seed material and machinery can disperse nematode populations.

**Life Cycle and Epidemiology**

In onion plants, its life-cycle takes about 20 days at 15°C. Females lay
200 - 500 eggs each. Fourth-stage juveniles tend to aggregate on or just
below the surface of heavily infested tissue to form clumps and often
termed as \"eelworm wool\" that can survive in a dry condition for
several years. They may also become attached to the seeds of host plants
(e.g. onions, lucerne, *T. pratense*, faba beans, *Phlox drummondii*).
In clay soils, *D. dipsaci* may persist for many years. Moist and cool
conditions generally favor invasion of young plant tissue by this
nematode. *D. dipsaci* spreads through dry seeds and planting material
of host plants.

**Management**

Management of *D. dipsaci* by crop rotation is confined by the
polyphagous nature of some of the races and by persistence of the
nematode in clay soils. Avoiding good host crops in rotation, wider row
spacing and proper weed control can reduce damage due to stem nematodes.
Nematicide treatments of soil are not an economic proposition for large
areas. However, it may sometimes be recommended for treating small
patches of nematode infestations under field conditions, to eradicate a
slight infestation before it spreads. Systemic nematicides have also
been found effective to some extent in controlling *D*. *dipsaci*.
Hot-water treatment with different temperature-time combinations,
depending on type and state of seed material, are operational and
efficient to control *D. dipsaci.* Tolerant or resistant cultivars
developed in various countries can also reduce the damage and can be a
part of successful breeding program.

Nematode-free (certified) seeds and planting materials that are also
free of soil contamination are essential to prevent crop damage by *D.
dipsaci*. Fumigation by methyl bromide at 32 g per cubic meter of seed
for 24 h at 28^o^C or equivalent or any other treatment was approved by
quarantine agencies. Suitable alternatives to this fumigant are now
needed in view of unavailability of methyl bromide due to environmental
concerns. The implementation of certification schemes for the production
of host plants of *D. dipsaci* can provide planting material free from
the pest. Imports of soil and plants for planting and seeds of host
plants from countries where this nematode occurs should be restricted.

**Selected References**

Bellar, M., and Kebabeh, S. 1983. A list of diseases, injuries and
parasitic weeds of lentils in Syria (survey 1979-1980). LENS 10: 30-31.

Beniwal, S. P. S., Bayaa, B., Weigand, S., Makkouk, K., and Saxena, M.
C. 1993. Field guide to lentil diseases and insect pests. ICARDA),
Aleppo, Syria. 107pp.

Greco, N., Di Vito, M., and Saxena, M. C.1992. Plant parasitic nematodes
of cool season food legumes in Syria. Nematologia Mediterranea 20:
37-46.

Sikora, R. A., Greco, N., and Silva, J. F. V. 2005. Nematode parasites
of food legumes. Pages 259-318 in: Plant parasitic nematodes in
subtropical and tropical agriculture. M. Luc, R. A. Sikora and J.
Bridge, eds. CABI Publishing, Wallingford, UK.

Vito, M. Di, Greco, N., Oreste, G., Saxena, M. C., Singh, K. B., and
Kusmenoglu, I. 1994. Plant parasitic nematodes of legumes in Turkey.
Nematologia Mediterranea 22: 245-251.

(Prepared by H. S. Gaur, Pankaj and K. K. Kaushal)