About endoparasitic nematode Ditylenchus dipsaci

1. SAM HIGGINBOTTOM UNIVERSITY OF AGRICULTURE TECNOLOGY
AND SCIENCE
Submitted To :-
Dr .Sobita Simon
H.O.D of Department of Plant Pathology
Submitted by
–K.Babji
M.Sc Plant Pathology (2nd SEM)
22MSAPP048
Course code-PLPY722
Course title-PLANT NEMATOLOGY

2. Migratory Endoparasitic Nematode
• Ditylinchus dispsaci

3. INTRODUCTION
Ditylenchus dipsaci is an internal parasite of
bulbs, stems, and leaves and passes
generation after generation in these tissues,
escaping to the soil only when living
conditions in the plant tissues become
unfavorable.

4. Scientific classification
Phylum – Nematoda
Class – Secernentea
Order – Tylenchida
Suborder – Tylenchina
Superfamily – Anguinoidea
Family – Anguinidae
Genus – Ditylenchus
Species – Ditylenchus dipsaci

5. Discovery
• Ditylenchus dipsci was first discovered by the
German botanist Julius Kuhn in 1857.Kuhn found
this nematode infesting Onion bulbs in German.
Initial classification
Kuhn initially classified the nematode as tylenchus
dipsaci, based on its morphological characteristics and its
association with the host plant, onion
Reclassification of ditylenchus dipsaci
Over time, further studies on the nematodes characteristics
, life cycle, and taxonomy led to its reclassification as
Ditylenchus dipsaci

6. Importance
• D. dipsaci shows parasitic adaptation in its ability to
invade solid parenchyma tissue following enzymatic
lysis of the pectic or middle lamella layer between
adjacent cell walls, leading to separation and
rounding of the cells. This causes the typical
glistening appearance or mealy texture of infested
tissues, reminiscent of the flesh of an over-ripe apple
(Southey, 1993).

7. Host range
D. dipsaci has an extensive host range. Major damage occurs in
garlic, onion, carrot, fava bean, alfalfa, oats, and strawberry.
Ornamental plants can also be infected including hyacinth and
tulip.[12] It is estimated that this pathogen infects 400–500
plant species worldwide.
In Allium species (onions, garlic, and leeks), infected
plants show characteristic symptoms including stunted
growth, yellow spots, leaf curl, and foliage lesions.
Stems often have swollen regions called “spikkles.” As
adult nematodes migrate into the scales of the bulb,
and the scales become soft, grey, and loosely packed.
Highly infected bulbs can also split apart or show
malformed bloating. The leaves of the plant become
flaccid and may collapse. This can lead to defoliated
plants.Garlic shows similar symptoms of leaf yellowing
and stunted bulbs. When harvested, the infected garlic
may be missing portions of the root system.
Symptoms

8. Survival absence of host
• The lifespan of stem and bulb nematodes is about 70
days. Most generations are passed inside bulbs, stems
and leaves. Eggs and larvae overwinter in dried
infected host material.They are also found in weed
hosts and seeds of composite. Stem and bulb
nematodes can survive up to two years in freezing or
extremely dry environments in the soil. D. dipsaci can
survive on or in plant tissue by
entering cryptobiosis and survive for 3–5 years in this
stage. During dormancy, D. dipsaci shows no sign of life
and the metabolic activity is almost at a standstill.

9. Life cycle
• Stem and bulb nematodes are migratory endoparasites. Their life
cycle occurs in five stages with the first molt occurring in the egg and
the second and third molt occurring in the soil. By the fourth stage
juveniles have entered the plant through young tissue and/or
seedlings. The fourth molt will then occur inside the plant. The adult
female must mate with a male to reproduce and lay eggs. A complete
reproductive life cycle of the stem and bulb nematode is 19-25 days
(egg to egg). Reproduction takes place in succulent, rapidly growing
tissues or in storage organs and continues throughout. A female can
lay 200-500 eggs in her lifespan. However if conditions are
unfavorable the nematodes can halt their life cycle. The life span of
stem and bulb nematodes is approximately 70 days. Most generations
are passed inside bulbs, stems and leaves. Eggs and larvae overwinter
in dried infected host material. They are also found in weed hosts and
seeds of composite. Stem and bulb nematode can survive up to two
years in freezing or extremely dry environments in the soil. D.
Dipsaci can survive on or in plant tissue by entering cryptobiosis
(hidden life) and survive for 3-5 years in this stage. During
dormancy D. Dipsaci shows no sign of life and the metabolic activity is
almost at a standstill.

11. Management
• Proper sanitation in fields and of tools is essential in preventing and
controlling the spread of D. dipsaci, because they can survive and
reproduce in infected plants and residues. The fourth-stage juvenile is the
most resilient and can survive repeated desiccation or drying and recover
upon rehydration. All infected tissues should be removed from growing
sites and destroyed to control populations, and all farm tools and
equipment should be cleaned of potentially contaminated soil before
moving them to a new location.
• The time a susceptible host crop is planted also infects the severity of
nematode damage. Cooler temperatures and lower humidity can suppress
the reproduction and infestation rates of D. dipsaci. Growers should avoid
planting susceptible bulbs, seeds, or seedling during seasons of peak
nematode infection. Soil fumigation in fields during fall can control
nematodes on a susceptible crop in the spring. A nematicide fumigant that
is specific to the genus Ditylenchus should be used. Selectively fumigate
only the regions of the fields that are infected to ensure that the high cost
of fumigating does not mitigate the economic gain from saving crops from
nematode damage. Fumigants are usually applied before planting and
subsequently after emergence.

12. THANK YOU