Nematodes and their Management

1. Nematode problem and its
mangement
Y. S. Chandel
Department of Entomology
CSKHPKV, Palampur-176062

2. What are nematodes?
• The word nematode is derived from Greek words- Nema
meaning thread and oides means resembling or forms.
• Nematodes are also known by different names such as
threadworms, roundworms, eelworms and nema.
• Nematodes constitute the largest group of animal kingdom
comprising 80-90% of all multicellular animals
• These organisms are basically aquatic but have adapted
terrestrial habits.

3. Where nematodes are found ?
Nematodes as a whole live under a variety of
conditions and are known to occur
everywhere where life can exist, from
arctics to tropics, from heights of mountains
to depths of oceans, they may be free-living
in soil or in water (fresh, marine and
brackish) or may live as parasites on
animals including man or on plants.

4. Parasites of man/animals
• Ascaris
• Hookworm
• Guinea worm
• Liverfluke etc.

5. Ascaris lumbricoidesAscaris lumbricoidesAscaris lumbricoides

6. Dracunculus medinensis

7. Plant parasitic nematodes
• The plant nematodes or phytonematodes are those
seen associated with plants and constitute one of the
most important groups of organisms which live in soil
around the roots of plants.
• Compared to human or animal parasitic nematodes like
filarial worm or ascaris, they are very small, about 0.01
to 1.00 mm in length. They are usually long and slender
excepting in the case of females of some sedentary
parasitic where they are enlarged and swollen and may
be spherical, oval, lemon-shaped or kidney-shaped.

11. Where nematodes are confined in agricultural soils ?
• In agricultural lands, plant nematodes are usually
confined to the top 20 to 25 cm of soil though this is
variable according to the type of soil, moisture
content , host plants and climatic conditions
• The citrus nematode, for instance, can occur at the
depths of 2 to 2.5 m and the burrowing nematode at
3 to 4m.
• The surface soil does not harbour any nematode,
since moisture and temperature fluctuate very widely
in this layer. In all cases the nematode distribution in
soil is governed by that of the host roots.

12. Mechanism of damage
• All plant parasitic nematodes possess a buccal
stylet or spear. It is a sharp pointed protrusible
organ which can be moved forth and back by
means of muscles attached to its base. It is used
to puncture the plant cells.
• Before sucking the sap the nematodes injects
some quantity of its saliva into the cell. The
enzymes contained in it predigest the cell
contents. It is phytotoxic in varying degrees in
different nematodes and is responsible for many
of the visible symptoms in the infected plants.

14. Ways of damage by nematodes in plants
As primary pathogens: In most cases plant nematodes are themselves primary
pathogens through draining of cell sap, dissolution and destruction of cells and
disorganization of conducting vessels of pants which are consequently
devitalized and show retardation of growth.
Association with other pathogens: Often nematodes are associated with other
pathogens like fungi, bacteria and viruses in causing diseases. It is well
established the role of nematodes in disease-complexes is more. The punctures
made by the nematodes are used by the microorganisms for entering in the
plant system.
Altering the host physiology: Nematodes can alter the physiology of the host in
such a manner that, when both nematode and fungus are present, the damage
caused by them is much more than that could be caused by the nematode or
the fungus when it occurs alone.
As vectors of virus diseases: Some species of nematodes are known to transmit
soil-borne viruses.

16. Life cycle
The plant nematodes have six stages, an egg,
four larval and an adult stage.
The larva undergoes first moulting inside the
egg itself and the second stage larva come out
to undergo three more moults before becoming
the adult.
The average number of eggs laid by a nematode
is about 200 to 500.
The life cycle is completed in 20 to 40 days in
many cases.

18. Why the nematode problem is severe in
polyhouses ?
• Congenial temperature(25-350
C)
• Availability of good moisture conditions in the
soil.
• Light soils

19. Some observation by the university
scientists
Total polyhouses analysed to know the gravity of
nematode problems = >450
Presence of mainly root knot nematode. Less
infestation in the newly started polyhouses.
High incidence of the nematodes is associated
either with crop failure or poor crop stand in
many cases.
Lack of proper knowledge to the farmers about
nematodes.

20. Sources of inoculums
• Through infested implements.
• Irrigation water
• Through insects

21. Above-ground Symptoms of nematode damage
1. Stunting: Stunting of plants is usually seen in patches.
2. Yellowing: Damage to the root system due to nematode feeding
adversely affects the uptake and translocation of nutrients upwards.
3. Wilting: Nematode damage to the vascular tissues disrupts the flow of
water to the foliage. This is most commonly noticeable in broad-leaved
plants. When leaves wilt during hot weather despite the presence of
enough moisture in the soil.
4. Dieback: In perennial crops like most fruit trees, general symptoms of
dieback, i.e. gradual shedding of foliage from tip downwards, premature
shedding of fruits, undersized fruits, weak seasonal flushes.
5. Dead or devitalized buds: Feeding on the terminal bud or the growing
point may result in a ‘blind’ plant, if it is totally destroyed e.g.
Aphelenchoides fragariae on strawberry.
6. Crinkling and curling of leaves: Constant irritation and ectoparasitic
feeding by the nematode on the newly emerging leaves.
7. Leaf spots, lesions: Foliar nematodes like Aphelenchoides ritzemabosi
enter through stomatal openings and feed on the mesophyll tissues of
leaves.

22. 3

23. Patchy growth due to Root Knot Nematodes
Okra

25. Below-ground symptoms
1. Root galls: The root-knot nematode, Meloidogyne species produce galls or
knots on the roots, which is very characteristic and diagnostic of this
nematode.
2. Reduced root system: Nematode feeding on the root tips may kill the growing
point and stop the further elongation of root.
3. Root lesions: Elliptical necrotic lesions are chiefly produced by lesion
nematodes, Pratylenchus spp. As the infection spreads, adjacent lesions may
coalesce and ultimately girdle the root making the terminal portion of the root
defunct.
4. Root rot : This is generally the result of secondary organisms which cause
decay of the fleshy underground tissues damaged by nematodes initially.
5. Excessive root branching: Nematode infection may sometimes stimulate the
plant to produce branch rootlets near the sites of penetration, resulting in
excessive root branching.
6. Swellings: Besides branching, the roots also show slight swellings at the sites
of nematode infection. Such roots appear bushy.

29. Roots infested with Root Knot Nematode (Meloidogyne incognita)
Brinjal Tomato

34. Management of nematodes in polyhouses
• Phytosanitary measures
• Soil testing for the nematodes at least twice in a year.
• Sampling methodology
• Raising of the healthy nursery
• Post harvest ploughing and maintenance of dry soil
conditions
• Do not keep the polyhouse open.
• Sterilization of implements used in other infested
polyhouse/fields before their use.
• Use of sufficient quantity of organic matter.
• Use of crop rotation, if possible.

35. Chemical Management
• Use of the nematicides- Carbofuran(Furadan 3 G)
OR Ethoprophos (Mocap) OR Prorate (Thimet 10G)
at the time of transplantation of crops in vegetable
crops in the soil having having nematode history.
• In carnation and other floricultural crops, the above
nematicides can be repeated at the interval of 1-2
months depending upon the nematode infestation.
• Treatment of the soil after the harvest of the crop
with Formalin.

36. Dazomet treated Metham sodium treated
Untreated